table of contents - New Hampshire Division of Forests and Lands

A Quick Overview of the NH Natural Heritage Inventory's Purpose and Policies 

The Natural Heritage Inventory is mandated by 

the Native Plant Protection Act of 1987 (NH RSA 

217-A) to determine protective measures and 

requirements necessary for the survival of native 

plant species in the state, to investigate the condition 

and degree of rarity of plant species, and to distribute 

information regarding the condition and protection of 

these species and their habitats. 

The Natural Heritage Inventory provides 

information to facilitate informed land-use decisionmaking. 

We are not a regulatory agency; instead, we 

work with landowners and land managers to help 

them protect the State's natural heritage and meet 

their land-use needs. 

The Natural Heritage Inventory has three facets: 

Inventory involves identifying new occurrences of 

sensitive species and classifying New Hampshire's 

biodiversity. We currently study more than 600 plant 

and animal species and 120 natural communities. 

Surveys for rarities on private lands are conducted 

only with landowner permission. 

Tracking is the management of occurrence data. Our 

database currently contains information about more 

than 4,000 plant, animal, and natural community 

occurrences in New Hampshire. 

Interpretation is the communication of Natural 

Heritage Inventory information. Our goal is to 

cooperate with public and private land managers to 

help them protect rare species populations and 

exemplary natural communities. 

cover: Red maple/Sphagnum saturated basin swamp in Northwood, NH 

Photograph by Daniel Sperduto 

This project was funded by the U.S. Environmental Protection Agency, 

with additional support from 

The Nature Conservancy, Association for Biodiversity Information, 

U. S. Forest Service, and National Oceanographic & Atmospheric Administration

TABLE OF CONTENTS 

Introduction..................................................................................................................................... 1 

NH Heritage Ecological Approach .................................................................................................1 

Natural Community Classification............................................................................................ 1 

Relationship of Natural Communities to Other Classifications................................................ 2 

Exemplary Natural Communities.............................................................................................. 4 

Rarity......................................................................................................................................... 4 

Quality Ranks............................................................................................................................ 6 

Size...................................................................................................................................... 7 

Condition............................................................................................................................. 7 

Landscape Context.............................................................................................................. 8 

Protecting New Hampshire's Biodiversity................................................................................ 9 

Methods......................................................................................................................................... 10 

Sources of Information............................................................................................................ 10 

Nomenclature .......................................................................................................................... 11 

Natural Community Descriptions ........................................................................................... 11 

New Hampshire Wetland Classification: Concepts and Organization ......................................... 12 

Five Broad Hydrogeomorphic Classes of Wetlands............................................................... 15 

Outline of the Classification Hierarchy................................................................................... 18 

Open Palustrine and River Channel Systems (non-peatlands)...................................................... 23 

Soligenous............................................................................................................................... 23 

Limnogenous........................................................................................................................... 26 

Topogenous/Limnogenous...................................................................................................... 32 

Aquatic Bed Communities............................................................................................................ 49 

Open Peatland Communities......................................................................................................... 51 

Mud-bottoms, Open Moss Lawns, and Flarks ........................................................................ 52 

Dwarf- and Medium-Shrub Bogs and Poor Fens.................................................................... 56 

Sedge and Shrub/Graminoid Fens........................................................................................... 61 

Tall – Medium Shrub Thicket/Sparse Woodlands.................................................................. 67 

Marshy Peatland-margin Communities .................................................................................. 71 

Forested Swamps and Floodplain Forests..................................................................................... 74 

Saturated/Seasonally Flooded Basin Swamps ........................................................................ 74 

Seepage Swamps and Mixed-Hydrology Swamps ................................................................. 84 

Forest Seeps ............................................................................................................................ 96 

Seasonally Flooded to Seasonally Saturated Swamps .......................................................... 104 

Temporarily Flooded/Seasonally Saturated Floodplain and Terrace Forests ....................... 107 

Vernal Pools................................................................................................................................ 128 

Estuarine Systems ....................................................................................................................... 129 

Intertidal Marshes ................................................................................................................. 129 

Intertidal Flats and Shores..................................................................................................... 144 

Subtidal Communities........................................................................................................... 147 

Literature Cited ........................................................................................................................... 150 

NH Natural Heritage Inventory 

iii

LIST OF TABLES 

Table 1. Explanation of global and state rank codes ...................................................................5 

Table 2. Trophic levels and approximate corresponding pH ranges in New peatland 

Hampshire community types.......................................................................................14 

Table 3. Organization of New Hampshire wetland natural community classification..............18 

Table 4. Outline of the Wetland Natural Communities of New Hampshire .............................19 

ACKNOWLEDGEMENTS 

I gratefully acknowledge a broad range of people and organizations that have contributed to 

making this effort possible. The influence of many people is reflected here, including their field 

data, advice, critical review, probing discussions, and ongoing support. This document is a 

reflection of – and is only possible as a result of – years of collaborative efforts and projects with 

these people and organizations. In addition to the direct involvement of those mentioned below, 

this document attempts to incorporate the work of a variety of vegetation researchers in the region. 

William Nichols contributed a substantial amount of valuable field work, data compilation, 

comments, and insights that have helped fill in many information gaps. I also especially thank 

Thomas Rawinski, Brett Engstrom, John Korpi, and Douglas Bechtel for their considerable 

wetlands community field work for NH Heritage; their findings have significantly advanced our 

knowledge of New Hampshire’s vegetation. Many years of thoughtful comments from and 

discussions with Thomas Lee, Mark Anderson, Thomas Rawinski, Brett Engstrom, Charles 

Cogbill, and Lesley Sneddon are particularly appreciated. Kathy Crowley and David VanLuven 

have provided valuable comments and editorial assistance. Alex Wong assisted with the 

compilation of data and draft descriptions for portions of an earlier version of this document. 

The earlier field work of many botanists and naturalists (Albion Hodgdon, Arthur S. Pease, 

Fred Steele, Clotilde Straus, Henry Baldwin, Frank Seymour, and many others) cannot be 

overstated in their contribution to the current understanding of New Hampshire’s flora. Natural 

Areas of New Hampshire Suitable for Ecological Research (Lyon and Reiners 1971) summarized 

many of the highlights of this earlier work. More recently, other botanists and ecologists have 

contributed significantly to our current knowledge of the flora and vegetation types of New 

Hampshire; these field researchers include Frankie Brackley-Tolman, William Leak, Thomas 

Lee, Garrett Crow, William Brumback, Debra Dunlop, Nur Ritter, Arthur Gilman, Rick van de 

Poll, David Boufford, and Gil George. Many thanks to Natalie Cleavitt for making significant 

contributions to documenting the bryophyte flora of New Hampshire. 

This compilation of wetland natural community descriptions was funded by the U.S. 

Environmental Protection Agency (EPA). Many of the descriptions are based on surveys 

conducted with more than 10 years of support from the EPA’s Wetlands Protection State 

Development Program. Other organizations that have provided partial funding for related past 

classification work include The Nature Conservancy, Association for Biodiversity Information, 

USDA Forest Service – White Mountain National Forest, and Office of State Planning/National 

Oceanographic and Atmospheric Administration. 

NH Natural Heritage Inventory 

iv

INTRODUCTION 

Natural communities are recurring assemblages of plants and animals found in particular 

physical environments. New Hampshire has a fascinating and complex variety of natural 

communities, from tidal marshes to alpine meadows, riverbanks to mountain slopes, streams to 

lakes. Each type of natural community has a unique set of environmental conditions that support 

certain species that have adapted to those conditions. For example, a rich hardwood forest 

typically has a canopy of sugar maple and white ash underlain by dutchman’s breeches, blue 

cohosh, and certain other plants, animals, and microbes. This natural community occurs on 

moist soils enriched with nutrients, and many of the species present grow only under these 

conditions. Pitch pine/scrub oak barrens, in contrast, develop on extremely dry sand and gravel 

deposits, and are characterized by drought- and fire-resistant pitch pine, scrub oak, low-bush 

blueberries, and a variety of rare moths and butterflies that feed on these plants. 

The NH Natural Heritage Inventory (NH Heritage) has been developing a classification of 

New Hampshire’s natural community types since 1986. This effort is an outgrowth of natural 

community classification work undertaken in the northeastern United States by The Nature 

Conservancy (Rawinski 1984), and ties into similar classifications under development by state 

natural heritage programs across the country. 

The primary goal of this project was to compile a statewide classification of the natural 

communities occurring within wetlands systems. This classification is intended to facilitate 

future surveys and to inform protection and management decisions concerning wetlands in New 

Hampshire. Funding for this study was provided by the U.S. Environmental Protection Agency. 

NH HERITAGE ECOLOGICAL APPROACH 

NATURAL COMMUNITY CLASSIFICATION 

NH Heritage classifies the landscape using "natural communities," which are recurring 

assemblages of species found in particular physical environments. Each natural community type 

is distinguished by three characteristics: 

1. a definite plant species composition; 

2. a consistent physical structure (such as forest, shrubland, or grassland); and 

3. a specific set of physical conditions (such as different combinations of nutrients, 

drainage, and climate conditions). 

Natural communities include both wetland types (e.g., red maple basin swamp) and uplands such 

as woodlands (e.g., rich red oak-sugar maple/ironwood talus forest/woodland) and forests (e.g., 

hemlock-beech-oak-pine forest). 

Our present understanding is inadequate to quantify all the important differences among 

natural communities. Consequently, some types are rather broadly defined and serve as catchall 

categories, while others are more precise. A broadly defined community type, such as “shrub 

swamp,” is likely to have greater differences in species composition from one example to 

NH Natural Heritage Inventory Page 1

another than those in narrowly defined types, such as red pine forests. Further, boundaries 

between natural community types can be either discrete (and therefore easily identified in the 

field) or gradual (thus making some areas difficult to map). 

Natural community types are usually defined in terms of plants because they are easy to 

study, often compose the physical structure to which most other organisms respond, and are 

sensitive indicators of physical and biological factors that influence many types of organisms. 

Since plant assemblages often correspond closely to other groups of organisms, they can be used 

as coarse filters that include many of the species and processes in a naturally community, even if 

they have not been specifically identified. 

Classifying natural communities enables ecologists, land managers, and others to 

communicate effectively and to make management decisions regarding ecological systems. 

Many classifications exist that define vegetation or other land units. In the following paragraphs, 

several of these are contra The classification of natural communities in New Hampshire is based 

on data from more than ten years of ecological research by ecologists with NH Heritage and The 

Nature Conservancy, plus extensive reviews of scientific literature. These data have been 

compiled and arranged into natural community types in part through the use of ordination and 

other statistical methods. Most state natural heritage programs continually update their 

classifications and cooperate with The Nature Conservancy's regional and national ecologists to 

ensure that natural community types are comparable across state lines. 

The names of natural community types generally begin with the dominant or most 

characteristic plant species, and may include the name of a landscape feature or vegetative 

structure that is typical of that community type. For example, black gum-red maple basin swamp 

refers to a basin swamp (a specific landscape feature, as opposed to a streamside swamp) with 

black gum and red maple in the canopy. In addition, like all Society of American Foresters 

forest cover types, forested natural communities may have considerable overlapping species and 

other characteristics, but they contain distinct and diagnostic combinations of species and 

physical characteristics. For example, the red spruce-northern hardwood natural community has 

considerably more red spruce in the overstory, and is generally higher in elevation, than the 

standard northern hardwood forest (sugar maple-beech-yellow birch forest natural community) 

despite many species that occur in both. 

A more detailed discussion of wetland concepts and the organization of the New Hampshire 

wetland classification hierarchy is presented in New Hampshire Wetland Classification: 

Concepts and Organization below. 

RELATIONSHIP OF NATURAL COMMUNITIES TO OTHER CLASSIFICATIONS 

In the following paragraphs, several other classification systems are contrasted with the 

natural community classification used by NH Heritage. 

At a national level, The Nature Conservancy has published a National Vegetation Classification 

System (Grossman et al. 1998; Anderson et al. 1998) that uses a formal classification hierarchy 


emphasizing differences in both vegetation structure and floristics. This system is periodically 

updated to include new information from more specific natural community classifications developed 

at the state level, such as the New Hampshire natural community classification. The Federal 

Geographic Data Committee has adopted a vegetation classification standard derived from the 

National Vegetation Classification for use by federal agencies, and future development of the 

classification is expected to be a collaborative effort (Grossman et al. 1998). This system crossreferences 

classifications produced and maintained by all state Heritage programs. 

While natural community names can be similar to the names of Society of American 

Foresters (SAF) forest cover types, natural communities are defined using a broader range of 

considerations. SAF forest cover types are primarily based on dominant tree species, while 

natural communities are based on all species, the structure of these species, and the specific 

physical environment. Trees are often subtle indicators of their environments. A number of 

natural communities can be distinguished based largely on trees, and in some cases differences in 

tree composition are the main difference between two community types. However, some trees 

are so broadly adapted that their presence does not precisely indicate site conditions (e.g., white 

pine or red maple). Differences in tree canopy composition may also primarily relate to cutting 

or other disturbances. 

For example, there are four SAF spruce-fir cover types that correspond to the "montane 

spruce-fir forest" natural community type. These different cover types primarily relate to stand 

disturbance history or the successional stage rather than to major environmental differences. The 

four cover types also do not differentiate between upland spruce-fir forests and spruce-fir 

swamps. When one considers understory species and soils, upland spruce-fir forests are 

markedly different from the red spruce/Sphagnum basin swamp natural community. In fact, the 

differences between these two natural communities are more dramatic than the internal 

differences between the four SAF spruce-fir cover types. SAF cover types are, however, useful 

for timber management. 

Natural community types and the U.S. Forest Service’s Ecological Land Types (ELTs), 

which to date have been defined only for National Forest lands, are not easily comparable for 

three primary reasons. First, ELTs are mapped at units of 100 or more acres, so some natural 

communities occur as smaller patches within various ELT types. Second, ELTs do not reflect 

major differences in soil nutrient status while natural communities do. Third, ELTs describe 

fine-scale soil characteristics that may have silvicultural significance but sometimes have no 

corresponding floristic expression. 

A classification scheme frequently used in wetland and aquatic systems was produced by 

Cowardin et al. (1979) for the U.S. Fish and Wildlife Service (USFWS). In the USFWS system, 

wetlands and deepwater habitats are defined by their vegetation, substrate, and frequency of 

flooding in a hierarchy that emphasizes flooding regimes and attributes of vegetation at a coarse 

scale (e.g., vegetation structure, life form, persistence, etc.). This classification system is useful 

because of its applicability to broad geographic regions and because it can be readily applied in 

conjunction with aerial photograph interpretation. It was the basis for wetland typing in the 

National Wetland Inventory mapping effort. 


Natural community types can typically nest within the hierarchical structure of the USFWS 

system. In addition to the flooding regimes and coarse vegetation characteristics used to 

distinguish USFWS types, however, the natural community classification also considers factors 

such as nutrient regime, water source, and geomorphic setting, as indicated by specific 

differences in floristic composition. For example, under the USFWS system, red 

maple/Sphagnum saturated basin swamps and red maple-black ash/swamp saxifrage seepage 

swamps would both be considered saturated, palustrine broad-leaved deciduous forested 

wetlands. This grouping does not reflect important differences between the two communities, 

including differences in species composition (ground cover by Sphagnum versus forb species), 

nutrient levels (species indicative of nutrient-poor versus minerotrophic conditions), water 

sources (upland runoff versus groundwater seepage), geomorphic settings (basin depression 

versus headwater seepage area), and soils (deep peat versus shallow peat over silt). The natural 

community classification provides additional detail regarding ecological conditions and 

processes that helps clarify the distribution of biological diversity across the landscape. 

EXEMPLARY NATURAL COMMUNITIES 

NH Heritage places particular emphasis on, and gives conservation priority to "exemplary" 

natural communities. Exemplary natural communities include all examples of rare types (such as 

a rich mesic forest) and high-quality examples of common types. High-quality natural 

communities are identified by having relatively little human impact. These areas have greater 

potential to contain or achieve natural dynamics that are characteristic of the original community 

types. A forested natural community need not be "old growth" to obtain exemplary status. 

Typical exemplary forested natural communities have a variety of characteristic species, natural 

regeneration within forested gaps, multiple age classes, diverse structural characteristics, 

abundant standing and fallen woody debris, intact soil processes, and little direct evidence of 

human disturbance. Such characteristics can only be studied, preserved, and understood by 

having appropriate reference sites. Further, exemplary natural communities represent the best 

remaining examples of New Hampshire's flora, fauna, and underlying ecological processes. 

The effects of the 1998 ice storm do not preclude any natural community from being designated 

exemplary. Damages caused by natural disturbances, including ice storms, blow-downs, and fire, 

are part the suite of natural processes influencing natural community dynamics. We take heavy ice 

damage into account when assessing natural communities, but if the community also displays 

exemplary attributes, including minimal human influence, then we are likely to classify it as such. 

RARITY 

NH Heritage considers the rarity of a natural community or a species both within New 

Hampshire and across its total range. We identify the degree of rarity within New Hampshire 

with a "State Rank" and throughout its range with a "Global Rank." Ranks are on a scale of 1 to 

5, with a 1 indicating critical imperilment, a 3 indicating that the species or natural community is 


Table 1. Explanation of global and state rank codes. 

Ranks describe rarity both throughout a natural community's or a species’ range (globally, or "G" rank) 

and within New Hampshire (statewide, or "S" rank). The rarity of sub-species and varieties is indicated 

with a taxon ("T") rank. For example, a G5T1 rank shows that the species is globally secure (G5) but the 

sub-species is critically imperiled (T1). 

Code Examples 

Description 

1 G1 S1 Critically imperiled because extreme rarity (generally one to five occurrences) or some 

factor of its biology makes it particularly vulnerable to extinction. 

2 G2 S2 Imperiled because rarity (generally six to 20 occurrences) or other factors demonstrably 

make it very vulnerable to extinction. 

3 G3 S3 Either very rare and local throughout its range (generally 21 to 100 occurrences), or 

found locally (even abundantly at some of its locations) in a restricted range, or 

vulnerable to extinction because of other factors. 

4 G4 S4 Widespread and apparently secure, although the species may be quite rare in parts of its 

range, especially at the periphery. 

5 G5 S5 Demonstrably widespread and secure, although the species may be quite rare in parts of 

its range, particularly at the periphery. 

U GU SU Status uncertain, but possibly in peril. More information needed. 

H GH SH Known only from historical records, but may be rediscovered. A G5 SH species is 

widespread throughout its range (G5), but considered historical in New Hampshire 

(SH). 

X GX SX Believed to be extinct. May be rediscovered, but evidence indicates that this is less 

likely than for historical species. A G5 SX species is widespread throughout its range 

(G5), but extirpated from New Hampshire (SX). 

Modifiers are used as follows. 

Code Examples 

Q 

Description 

G5Q GHQ Questions or problems may exist with the species' or sub-species' taxonomy, so more 

information is needed. 

G3 3 The rank is uncertain due to insufficient information at the state or global level, so 

more inventories are needed. When no rank has been proposed the global rank may be 

"G" or "G5T" or it may be left blank 

When ranks are somewhat uncertain or the species' status appears to fall between two ranks, the ranks 

may be combined. For example: 

G4G5 

G5T2T3 

G4Q 

G3G4Q S1S2 

The species may be globally secure (G5), but appears to be at some risk (G4). 

The species is globally secure (G5), but the sub-species is somewhat imperiled (T2T3). 

The species appears to be relatively secure (G4), but more information is needed to 

confirm this (). Further, there are questions or problems with the species' taxonomy 

(Q). 

The species is globally uncommon (G3G4), and there are questions about its taxonomy 

(Q). In New Hampshire, the species is very imperiled (S1S2). 


uncommon, and a 5 indicating that the species or natural community is common and 

demonstrably secure (see Table 1 for more details). Species and natural communities considered 

to be “globally rare” or “state rare” are those designated G1-G3 or S1-S3, respectively. Some 

species are rare both globally and in New Hampshire (e.g., G2 S1), while others are common 

elsewhere but rare in New Hampshire (e.g., G5 S1). Many communities have not been assigned 

global ranks at this time, pending a comprehensive review of their status and distribution rangewide. 

QUALITY RANKS 

In addition to considering the rarity of a natural community or species as a whole, NH 

Heritage ranks the quality of individual natural community occurrences and rare plant 

populations. These "Quality Ranks" give a more detailed picture of significance and 

conservation value. Quality ranks are based on the size, condition, and landscape context of a 

natural community or rare species population. These terms collectively refer to the integrity of 

natural processes or the degree of human disturbances that may sustain or threaten long-term 

survival. There are four quality ranks: 

Rank 

A 

B 

C 

D 

Description 

Excellent Occurrence: An A-ranked natural community is a large example nearly 

undisturbed by humans or which has nearly recovered from early human disturbance and 

will continue to remain viable if protected. An A-ranked rare species occurrence is large 

in both area and number of individuals, is stable, exhibits good reproduction, exists in a 

natural habitat, and is not subject to unmanageable threats. 

Good Occurrence: A B-ranked community is still recovering from early disturbance or 

recent light disturbance by humans and/or may be too small in size to be an A-ranked 

occurrence. A B-ranked population of a rare species occurrence is at least stable, grows 

in a minimally human-disturbed habitat, and is of moderate size and number. 

Fair Occurrence: A C-ranked natural community is in an early stage of recovery from 

disturbance by humans and/or a small sized representative of the particular type of 

community. A C-ranked population of a rare species is in a clearly human-disturbed 

habitat and/or small in size and/or number, and possibly declining. 

Poor Occurrence: A D-ranked natural community is severely disturbed by humans, its 

structure and composition are greatly altered, and recovery is unlikely. A D-ranked 

occurrence of a rare species is very small, has a high likelihood of dying out or being 

destroyed, and exists in a highly human-disturbed and vulnerable habitat. 

For example, consider a population of a rare orchid growing in a bog that has a highway running 

along one border. The population may be large and apparently healthy (large size and intact 

condition), but the long-term threats posed by disturbance at the bog's edge – its low-quality 

landscape context (pollution from cars and roads, road-fill, garbage, altered hydrology, reduced 

seed dispersal, etc.) – may reduce the population's long-term viability. Such a population of 


orchids would receive a lower rank than a population of equal size and condition in a bog 

completely surrounded by a forest (i.e., with a higher quality landscape context). 

NH Heritage, in collaboration with other state heritage programs and The Nature 

Conservancy, is working to develop quality rank specifications for all of New Hampshire's 

natural communities and rare plant species. Unfortunately, limited time and incomplete 

knowledge, both on local and global scales, have prevented the development of thoroughly tested 

and peer reviewed quality rank specifications for most of New Hampshire's natural communities 

and rare species. 

In the absence of rank specifications for each natural community, NH Heritage uses broad 

guidelines for assigning preliminary quality ranks. The guidelines for assessing the size, 

condition, and landscape context for natural communities are described below. 

SIZE 

Occurrence size is a quantitative measure of area occupied by a species or natural community 

and accounts for such factors as population abundance, fluctuation, density, and area of 

occupancy for species. All else being equal, the larger a natural community is, the more viable it 

will be. Large size is correlated with increased heterogeneity of internal environmental 

conditions, integrity of ecological processes, species richness and size of constituent species 

populations and their respective viability, potential resistance to change, resilience against 

perturbations, and ability to absorb disturbances. Size is used in a relative sense with respect to 

the range of sizes exhibited by the particular natural community type. 

CONDITION 

Condition is a combined measure of the quality of reproduction (for species), 

development/maturity (for communities), degree of integrity of ecological processes, species 

composition, biological and physical structure, and abiotic physical factors within the 

occurrence. For example, old growth forests with little anthropogenic disturbance and intact 

biotic and abiotic factors, structures, and processes, would warrant an "A" rank for condition 

regardless of size. 

1. Excellent Condition: Old growth or minimally disturbed by human impacts with recovery 

essentially complete, or in the case of disturbance-maintained communities (e.g., pitch 

pine/scrub oak barrens), the natural disturbance regime has prevailed continuously with no 

significant or irreversible alterations by humans; ecological processes, species composition, 

and structural features are intact. 

2. Good Condition: Mature examples with only minor human impacts or good potential for 

recovery from relatively minor past human impacts; ecological processes, species 

composition, and structural features are largely intact. 


3. Fair Condition: Immature examples or those with significant human impacts with 

questionable recovery potential or in need of significant management and/or time to recover 

from present condition; ecological processes, species composition, and structural features 

have been altered considerably but not to the extent that the occurrence is no longer viable if 

managed and protected appropriately. 

4. Poor Condition: Little long term viability potential. 

LANDSCAPE CONTEXT 

Landscape context is a combined measure of (a) the quality of landscape structure, (b) the 

extent (including genetic connectivity), and (c) the condition of the surrounding landscape that 

influences the occurrence's condition and viability. Dynamic natural community occurrences, 

including many open natural community types in the Coastal Lowland Subsection, have a better 

long-term viability when they are associated with large areas of diverse habitat that support 

dynamic ecosystem processes. Potential factors to be considered include: (a) the degree of 

landscape fragmentation; (b) the relationship of a natural community to contiguous wetland or 

upland natural communities; (c) the influence of the surrounding landscape on susceptibility to 

disturbance; (d) the relative position in a watershed; (e) susceptibility of the occurrence to 

pollutants and hydrologic change (Chase et al. 1995); and (f) the functional relationship of the 

natural community to surrounding natural landscape features and larger-scale biotic and abiotic 

factors. For example, open peatlands are extremely sensitive to nutrient input, basin swamps are 

moderately sensitive, and streamside/riverside communities and seepage swamps are less 

sensitive. 

In general, landscape condition is weighted towards the immediate 30-300 m (100-1000 ft.) 

buffer area around the natural community where direct impacts of land use may be most 

significant. The adjacent 1.6-3.2 km 2 (1-2 mi 2 ) area or relevant watershed area around the 

natural community is considered to a lesser degree. In turn, the larger area around that receives 

the least consideration. The actual size applied for a natural community varies according to the 

characteristics of the particular natural community and the specific context of the occurrence in 

the landscape. 

1. Excellent Landscape Context: Natural community is embedded in a matrix of undisturbed, 

unfragmented surrounding natural communities that have functional connectivity to the 

occurrence; past human disturbances that potentially influence the community are minimal or 

negligible. 

2. Good Landscape Context: Surrounding landscape is largely intact and minimally 

fragmented, or human disturbance/fragmentation is of a configuration and magnitude that is 

consistent with maintaining the current condition of the occurrence, or disturbances can be 

managed to achieve viability. 


3 Fair Landscape Context: Significant human impacts, development, fragmentation, and 

other disturbances characterize the landscape around the natural community and may affect 

the long term viability and condition of the occurrence. 

4. Poor Landscape Context: Functional human impacts, fragmentation and loss of natural 

communities dominate the surrounding landscape; the occurrence is probably not viable, 

even with management. 

PROTECTING NEW HAMPSHIRE'S BIODIVERSITY 

In 1994, the Northern Forest Lands Council (1994) concluded that "maintaining the region's 

biodiversity is important in and of itself, but also as a component of stable forest-related 

economies, forest health, land stewardship, and public understanding." In response to 

recommendations by the Northern Forest Lands Council, the NH Division of Forests & Lands 

and the NH Fish & Game Department established the Ecological Reserves System Project. One 

of the project's primary objectives was to "assess the status of biodiversity in New Hampshire 

and the extent to which it is protected under the current system of public and private 

conservation lands" (NH Ecological Reserve System Project 1998b). This question was then 

explored by a 28-member Scientific Advisory Group who took the question beyond the Northern 

Forest and considered it in a statewide context. The conclusions of the group indicated that there 

was a serious need for continued biodiversity conservation in New Hampshire: 

Though conservation lands comprise approximately 20% of the land area in New 

Hampshire, the current system of conservation lands in New Hampshire does not appear 

to provide comprehensive, long-term protection of biodiversity at the species, natural 

community, or landscape levels (NH Ecological Reserve System Project 1998a). 

NH Heritage strives to facilitate protection of the state's biodiversity through the protection 

of key areas that support rare species, rare types of natural communities, and high quality 

examples of common natural community types. Exemplary natural communities are particularly 

important because we assume that if we protect an adequate number of viable examples of each 

natural community type, we can protect the majority of New Hampshire's species. This is 

sometimes referred to as a "coarse filter" approach to protecting biodiversity. 

The "coarse filter" can miss important species, however, so it needs to be augmented with a 

finer filter. The "fine filter" approach generally focuses on specific rare species. For example, 

the rare, federally threatened Isotria medeoloides (small whorled pogonia) occurs in a variety of 

second-growth hardwood forests in southern New Hampshire. This orchid’s habitat may not be 

captured by the coarse filter approach, so we need to employ a fine filter approach (i.e., survey 

for the plant itself) to ensure that the species is protected. 

Long-term protection of New Hampshire's species, natural communities, and ecological 

processes requires a variety of conservation approaches. The goal of NH Heritage's coarse and 

fine-filter approaches is to inform management decisions by identifying those sites that have a 

relatively greater potential for maintaining the natural diversity within the state. 


The foundation for successful biodiversity protection is a series of representative, highquality 

examples of all the state's natural community types, with their constituent species and 

their underlying ecological processes. The best option for this kind of protection would be a 

series of connected, high quality natural community types; this series would ensure that 

ecological processes that connect natural communities remain functionally intact within a 

broader landscape context. In short, there is a need for reserve areas with natural communities 

protected within a diverse landscape, not just in isolation. 

METHODS 

SOURCES OF INFORMATION 

This document represents a thorough compilation of wetland community classification work 

performed by NH Heritage. Community descriptions have been compiled from numerous reports 

on specific groups of wetland communities, many of which have been funded by the Environmental 

Protection Agency. These reports are listed below and referenced in the document as appropriate. 

In addition to descriptions compiled from these published sources, many community descriptions 

(e.g., estuarine communities, boreal swamps, forest seeps and several others) were developed and 

refined specifically for the purposes of this document. Details regarding classification and field 

methodology are contained in the specific documents listed below. 

• Alpine and Subalpine Vegetation of the White Mountains, New Hampshire (Sperduto and 

Cogbill 1999) 

• Atlantic White Cedar Wetlands of New Hampshire (Sperduto and Ritter 1994) 

• Black Gum (Nyssa sylvatica Marsh) in New Hampshire (Sperduto et al. 2000) 

• Bogs and Fens of New Hampshire (Sperduto et al. 2000) 

• Calcareous Fens and Riverside Seeps in New Hampshire (Sperduto and Gilman 1995) 

• A Classification of the Natural Communities of New Hampshire (Sperduto 1994a) 

• Coastal Plain Pond Shores and Basin Marshes in New Hampshire (Sperduto 1994b) 

• Floodplain Forest Natural Communities along Major Rivers in New Hampshire (Bechtel and 

Sperduto 1998) 

• Floodplain Forest Natural Communities along Minor Rivers and Large Streams in New 

Hampshire (Nichols et al. 2000) 

• A Guide to the Natural Communities of New Hampshire, Interim version (Sperduto 1997b) 

• Northern White Cedar Swamps of New Hampshire (Sperduto and Engstrom 1998) 

• A Preliminary Classification of Natural Communities in the New Hampshire Coastal 

Lowlands Ecoregion (Sperduto 1997a) 

• The Vegetation of Seasonally Flooded Sand Plain Wetlands of New Hampshire (Sperduto 2000). 


NOMENCLATURE 

Because of the ongoing evolution of plant taxonomy, vascular plant nomenclature in this 

document follows two principal authorities. In descriptions prepared in or before 1997, 

nomenclature generally follows Fernald (1950) and Seymour (1993). In descriptions prepared 

after 1997, nomenclature follows Gleason and Cronquist (1991) and occasionally Fernald 

(1950), with common names generally following George (1998). Nomenclature will be 

standardized in a future revision of this document. 

Nomenclature of non-vascular species generally follows Crum (1981) and Cleavitt (1995). 

Nomenclature of Sphagnum species follows Cleavitt et. al. (In press). 

NATURAL COMMUNITY DESCRIPTIONS 

Community descriptions in this document follow two formats, based on the format of the 

document in which each description originated: (1) paragraph style, and (2) divided into 

subsections. Where subsections are used within a description, they follow the format below: 

COMMUNITY NAME: The "common name" of the natural community, often referring to the 

geographic region (e.g., Appalachian), primary associated habitat or landform, and/or major 

dominant or characteristic plants. Though many of the names sound like cover types, they 

usually represent a suite of associated species and habitat characteristics not present in the name. 

Under the common name of each community, the “technical” plant association name is 

frequently given. The plant association name identifies the community by primary dominant and 

characteristic species. A hyphen (-) is used to separate species within the same strata (tree, 

shrub, herb, non-vascular), whereas a slash (/) is used to separate strata. 

NH Heritage rarity ranks are listed after each natural community name. Global ranks (such 

as G3) have only been determined for a few communities, while state ranks (such as S3) have 

been assigned to all communities. Ranks range from 1-5, with a 5 indicating that the community 

is demonstrably secure either globally or in the state, while a 1 indicates “critically imperiled” 

either globally or in the state (generally 1-5 occurrences). See Table 1 for an expanded 

explanation. 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: "Word-picture" or concept behind the 

community, including discussion of important ecological processes (e.g., flooding, fire, erosion, 

etc.) 

SOILS/GEOLOGY/HYDROLOGY: Information on the influence or characteristics of soils, geology, 

and hydrology, including the prevailing nutrient regime. 

CHARACTERISTIC VEGETATION: Dominant and diagnostic (characteristic, differential, and 

indicator) species. Rare species tracked by the NH Heritage are noted with an asterisk (*). 


DISTRIBUTION: Distribution in New Hampshire, including elevation range and ecoregion 

subsections 1 in which the community is present. 

COMMENTS: Comments on distinctiveness of community, confidence in rarity rank, 

completeness of information, and whether the type as described includes much variation (and 

potentially more than one community) or if it is narrowly defined and not likely to include 

considerably more variation than presently understood. 

GOOD EXAMPLES: Examples of good occurrences of the community type in New Hampshire, 

primarily on public land or private land with public access. 

SOURCES: Sources used in completing descriptions. 

NEW HAMPSHIRE WETLAND CLASSIFICATION: CONCEPTS AND ORGANIZATION 

The classification of wetlands has been approached in numerous ways. In this document, we 

define wetland natural community types based on species composition, vegetation structure, and 

environmental attributes. We use different hydrogeomorphic and nutrient regime categories to 

organize these communities within a nested hierarchy (rather than using vegetation 

characteristics alone). This groups communities together that occur in similar landscape settings 

or that have similar physical characteristics. 

There are five major wetland attributes that are referred to repeatedly in the community 

descriptions and that are used to organize the classification hierarchy. These are (1) geomorphic 

setting, (2) water source, (3) hydrodynamics, (4) trophic regime, and (5) species composition and 

physiognomy. All five are summarized below. The first three are discussed in more detail in 

Brinson (1993). Following the discussion of these five attributes, we describe five broad 

hydrogeomorphic types of wetlands present in New Hampshire that represent different 

combinations of the five attributes. 

1. Geomorphic setting: The internal characteristics or “forcing functions” of a wetland are 

often determined by factors beyond its boundaries, particularly the landscape or geomorphic 

setting. Major geomorphic categories include depressional or basin wetlands, extensive 

peatlands, riverine wetlands, and fringe wetlands (such as tidal communities). 

2. Water source: There are three primary water sources in wetlands: precipitation, surface or 

near surface flow, and groundwater (including groundwater seepage). These combine in 

different proportions and vary temporally, affecting hydrodynamics and nutrient regimes of 

1 

Ecoregions are landscape divisions used by The Nature Conservancy and Natural Heritage programs nationwide 

that cover tens of thousands of square miles and have similar biological and physical characteristics – particularly 

climate, topography, and soils – and broad distribution patterns of plants and animals (Anderson et al. 1999). New 

Hampshire lies within three ecoregions: Northern Appalachian/Boreal Forest; Lower New England/Northern 

Piedmont; and North Atlantic Coast. Ecoregions consist of aggregations of finer-scale subsections (see below) that 

share numerous natural communities uncommon in or absent from adjacent ecoregions. 

Subsections are components of ecoregions that contain similar geologic substrates, soils, and vegetation (Keys 

et al. 1995). They are much smaller than ecoregions, with all or portions of nine subsections occurring within 

New Hampshire. 


wetlands. For instance, the greater the proportional contribution of precipitation to the 

annual water budget of a wetland, the more nutrient poor it is likely to be. Wetlands 

influenced by more surface or groundwater flow are more minerotrophic. The resulting 

nutrient regime within a wetland will depend in part on the mineral composition of the soil or 

bedrock that the water flows through. 

3. Hydrodynamics: This refers to the motion of water and its capacity to do work. Water flow 

can be vertical (e.g., precipitation and evapotranspiration), unidirectional (e.g., stream flow), 

or bi-directional (e.g., tidal flow in estuarine systems). Differences in the seasonality, 

frequency, intensity, and duration of water table fluctuations and flooding have dramatic 

effects on species composition and wetland functions. The USFWS system by Cowardin et 

al. (1979) has flood regime classes that integrate some, but not all, of these hydrodynamics. 

The USFWS classification of wetlands is based primarily on the vegetation structure 

(e.g., forest, scrub-shrub, emergent), vegetation morphology (e.g., coniferous, deciduous, 

persistent emergent, etc.), water regime, and substrate. The water regime classes and the 

corresponding general groups of wetland natural communities described in the New 

Hampshire classification are as follows: 

Permanently flooded 

Intermittently exposed 

Semi-permanently flooded 

Saturated 

Seasonally flooded 

Riverine, lacustrine, and aquatic bed communities 

Aquatic bed and deep emergent marshes 

Aquatic bed, deep, and moderate depth emergent marshes 

Bogs, fens, seepage marshes, seepage swamps, and some 

basin swamps 

Shallow to moderate-depth emergent marshes, shrub 

thickets, streamside/lakeside swamps, and some basin and 

seepage swamps 

Temporarily flooded Floodplain forests, open river channel and floodplain 

thickets, meadows, and barrens, shrub thickets, and some 

swamps and “low woods” 

An additional flood regime is used to describe some New Hampshire natural 

communities (see Golet et al. 1993): 

Seasonally saturated Some basin and seepage swamps, mineral soil swamps, and 

“low woods” along drainages 

The flood regime classes and other attributes of the USFWS classification are very useful 

descriptors for wetlands and are used throughout the New Hampshire classification 

document. However, the USFWS system alone does not directly integrate several important 

attributes we refer to frequently in the New Hampshire classification including geomorphic 

setting and water source (discussed above) and trophic regime and species composition 

(discussed below). In part, this is because these attributes are not readily inferred from air 

photos. 


Trophic Level Relative Acidity Approximate pH Range 

Oligotrophic 

Very acidic 

Acidic 

7.3 

Table 2. Trophic levels and approximate corresponding pH ranges in New Hampshire 

peatland community types. 

4. Trophic regime: Trophic regime is an important determinant of species composition in all 

wetlands. Water source, geomorphic setting, and hydrodynamics exert considerable control 

on the availability of nutrients within a wetland. However, the mineral composition of 

bedrock and soil through which water flows has a significant modifying affect on nutrient 

content of the water entering a wetland. Differences in trophic regime can be inferred from 

species composition, pH, vegetation height, micro-relief (hummock-hollow development), 

soil texture, and degree of decomposition of peat in organic soils, among other wetland 

characteristics. Variation in these factors is closely associated with different community 

types. For example, a dwarf shrub layer (

indicate a high availability level for all nutrients. While base-cations are in short supply in 

very acidic soils, aluminum levels can be high enough to have a toxic effect on some plants. 

Finally, pH and trophic regime can vary dramatically at a fine scale within a wetland, such as 

the transition from a hummock to an adjacent hollow. 

5. Species composition and physiognomy: Plant species are sensitive indicators of environmental 

conditions. Specific plant species and species assemblages are used throughout the classification 

to define communities and to indicate the hydrologic conditions and nutrient regimes described 

above (in addition to direct observations of these attributes). These species-environment 

associations are based on both quantitative and qualitative analyses within New Hampshire and 

well-established relationships published in floras and other literature elsewhere. 

The physiognomy (structure and life-forms) of vegetation also infer a great deal about the 

environmental conditions. Natural communities are often characterized by plants that have 

similar adaptive traits, such longevity (annual vs. perennial), reproductive strategy (vegetative 

vs. seed), density (matrix-forming dominants vs. interstitial species), height, and life form (tall 

shrub, tall forb, short graminoid, etc.). We use these attributes in classifying and describing 

natural communities. 

Statewide inventories of wetlands by NH Heritage and others have helped determine the 

distribution and abundance of each specific wetland type within the state. From this information, 

we are able to assess the rarity and significance of each type. 

FIVE BROAD HYDROGEOMORPHIC CLASSES OF WETLANDS 

At a very coarse scale, all five wetland attributes (outlined above) can be integrated to 

describe five broad classes of wetlands (outlined below) that emphasize the dominant source and 

characteristics of water affecting a wetland. These classes are often associated with particular 

landscape positions and water regimes, but intermediate forms can be identified. All five classes 

contain open and forested natural communities. More detailed studies are needed to link specific 

vegetation composition to hydrologic profiles and water sources. 

1. River channel and floodplain communities (limnogenous): These communities occur on 

alluvial mineral sediments in periodically flooded bottomlands adjacent to major rivers and 

large streams. Sediments accumulate in active river channels and on floodplain terraces 

above bankfull flood stage (bankfull flood occurs on average every 1-2 years). Flood and 

saturation regimes vary according to elevation above the watercourse, channel 

characteristics, watershed size, and landscape setting. While some river channel and high 

floodplain communities do not have hydric soils (e.g., gravel barrens), we have chosen to 

treat them collectively along with other floodplain communities because they are an integral 

part of the aquatic-terrestrial interface that occurs between rivers and adjacent uplands. All 

of these communities are demonstrably affected by the flood dynamics of the river. Most 

river channel and floodplain forests are temporarily flooded but vary in terms of the intensity, 

frequency, and timing of floods. Soil texture is determined by intensity of the flood regime 

and affects water availability. 


Common floodplain plants include Acer saccharinum (silver maple), Acer rubrum (red 

maple), Prunus serotina (black cherry), Quercus bicolor (swamp white oak), Ulmus americana 

(American elm), Carpinus caroliniana var. virginiana (musclewood), Spiraea alba (meadowsweet), 

Matteuccia struthiopteris var. pensylvanica (ostrich fern), Onoclea sensibilis (sensitive 

fern), Solidago rugosa (rough goldenrod), Euthamia graminifolia (grass-leaved goldenrod), 

Eupatorium maculatum (spotted Joe-pye-weed), and Calamagrostis canadensis (blue-joint). 

2. Seepage wetlands (soligenous): Seepage wetlands are influenced by groundwater seepage 

(discharge) in the form of subsurface flow into a wetland, sometimes as springs. Perennial 

groundwater sources tend to moderate water fluctuations and maintain conditions favorable 

for the accumulation of organic matter, though to a lesser extent than in stagnant basin 

swamps with less through-flow. Seepage wetlands occur in many landscape positions 

including headwater streams or basins, along the margins of large wetlands, and where water 

is forced to the surface by an impervious soil layer. Some peatlands (fens) have a reliable 

source of groundwater seepage and are referred to as soligenous. Generally they are 

characterized by significant organic soil development and relatively little alluvial influence 

(although streams may be present). Seepage water that is influenced by the nature of the 

parent material or underlying soils it passes through is termed minerotrophic and can produce 

enriched conditions in some situations (i.e., where underlying glacial deposits are 

intermediate/circumneutral or basic/calcareous). The terms circumneutral and calcareous are 

used here to infer enriched, minerotrophic conditions that are at the middle to higher end of 

the range of pH and nutrient availability gradient found in New Hampshire. 

Seepage conditions can be indicated by the presence of certain plant species [Rawinski 

(1983b) and this document]. Seepage indicators are most readily evident where seepage is 

pronounced or dominates the hydrologic inputs, and may be absent in swamps where seepage 

inputs form a relatively small proportion of the water budget. Indicator plant species include 

Lindera benzoin (spicebush), Fraxinus nigra (black ash), Lonicera villosa (mountain-flyhoneysuckle), 

Geum rivale (purple or water avens), Saxifraga pensylvanica (swamp saxifrage), 

Senecio robbinsii (Robbin's ragwort), Senecio aureus (golden ragwort), Scirpus microcarpus 

(red-tinged bulrush), Equisetum sylvaticum (wood horsetail), Mitella nuda (naked miterwort), 

Caltha palustris (marsh marigold), Lysimachia thyrsiflora (tufted loosestrife)*, Platanthera 

clavellata (green woodland orchis), Platanthera psycodes (purple-fringed orchid), Platanthera 

grandiflora (large purple fringed orchid), Pyrola secunda (one-sided pyrola), and certain 

sedges (e.g., Carex hystericina, Carex interior (inland sedge), Carex bromoides, and Carex 

diandra, among others). Plants usually indicative of enriched groundwater seepage influence 

(calcareous or circumneutral conditions) include Cardamine bulbosa (bulbous bittercress)*, 

Potentilla fruticosa (shrubby cinquefoil), Cypripedium reginae (showy lady's slipper)*, 

Cypripedium pubescens (large yellow lady's-slipper)*, Cypripedium parviflorum (small yellow 

lady's-slipper)*, Liparis loeselii (Loesel's twayblade)*, Rhamnus alnifolia (alder-leaved 

buckthorn), Petasites frigidus var. palmatus (sweet coltsfoot)*, Listera convallarioides (lilyleaved 

twayblade)*, Valeriana uliginosa (swamp valerian)*, Conioselinum chinense (hemlock 

parsley), and Calypso bulbosa (Calypso orchid)*. 


3. Basin wetlands (topogenous): Basin wetlands form in topographically defined depressions 

with stagnant or poor drainage and relatively little or no seepage or alluvial influence. Most 

examples are peatlands, such as bogs, fens, and forested swamps. Precipitation and seasonal 

subsurface runoff from small surrounding watersheds are the primary water sources, while 

evapotranspiration is the primary source of seasonal water table fluctuation. Consequently, 

nutrient poor and acidic conditions prevail. Organic muck and peat soils typically 

accumulate due to the lack of aeration and the presence of cold, acidic conditions. The most 

common water regime classes are saturated and seasonally flooded. Stream inlets are small, 

intermittent, or absent. Stream outlets are common, but there are usually no streams through 

the wetland (when present they are small and stagnant). Many species in basin wetlands 

occur in other settings as well, but the overall diversity of plants is generally lower than in 

seepage and streamside/lakeside swamps. 

Frequent swamp trees include Acer rubrum (red maple), Tsuga canadensis (hemlock), 

Picea rubens (red spruce), Picea mariana (black spruce), Larix laricina (eastern larch), 

Chamaecyparis thyoides (Atlantic white cedar), Thuja occidentalis (northern white cedar), 

and Nyssa sylvatica (black gum). Common shrubs and herbaceous plants include 

Chamaedaphne calyculata (leather-leaf), Vaccinium corymbosum (highbush blueberry), 

Nemopanthus mucronata (mountain holly), Kalmia angustifolia (sheep laurel), Ilex spp. 

(winterberries), Cornus canadensis (bunchberry), Coptis groenlandica (goldthread), 

Gaultheria hispidula (creeping snowberry), Osmunda cinnamomea (cinnamon fern), and 

Carex trisperma (three-seeded sedge). Species indicative of more minerotrophic conditions 

such as Onoclea sensibilis (sensitive fern), Carex stricta (tussock sedge), and Calamagrostis 

canadensis (blue-joint) are generally absent. 

4. Streamside/lakeside wetlands (limnogenous): Limnogenous wetlands are influenced by 

fluctuations of water levels associated with streams, rivers, and lakes (e.g., streambank 

overflow or lake water seiches). These wetlands are typically seasonally flooded. Soils in 

streamside and lakeside wetlands are well-decomposed muck or mucky mineral soils. This is 

in contrast to mineral soils on river floodplains and peat soils in basin settings. However, 

they do not exhibit the degree of alluvial sedimentation of floodplain forest soils as indicated 

by greater organic matter content of soils. These wetlands are subject to significant water 

level changes over the course of decades and centuries that result from natural and human 

impoundments (e.g., beaver dams, log jams, and human dams). As a result, many examples 

are successional, with transitions from aquatic bed to marsh to swamp occurring as 

sedimentation and organic matter build-up follow impoundment and flooding. 

Species such as Spiraea alba (meadow-sweet), Alnus incana var. americana (speckled alder), 

Carex stricta (tussock sedge), Calamagrostis canadensis (blue-joint), and a diverse array of 

other emergent and aquatic species are common in streamside and lakeside swamps and marshes. 

5. Mixed-hydrology wetlands: Seepage, basin, and streamside/floodplain (alluvial) wetlands are 

characterized by the dominance of one of the primary water sources; groundwater, precipitation, 

and surface or near surface flow, respectively. However, many swamps have a considerable 

proportion of their hydrologic budget contributed by more than one or all three primary water 


sources. As such, they are not readily categorized as classic examples of seepage, basin, 

streamside, or floodplain swamps. For this reason, some swamps are intermediate between the 

four other classic broad types discussed above. For example, some swamps occur in moderate to 

large open-basin settings that are influenced upland runoff and some streambank overflow, but 

are also supplied with groundwater discharge. Streams that may occur in these swamps are 

generally not large enough to be the dominant source of water level fluctuations. 

Species composition is similar to basin swamps but at least some indicators of more 

minerotrophic conditions are present. These include Alnus incana var. americana (speckled 

alder), Onoclea sensibilis (sensitive fern), Chelone glabra (white turtlehead), Arisaema 

triphyllum var. triphyllum (common Jack-in-the-pulpit), Symplocarpus foetidus (skunk 

cabbage) or any of the seepage indicators listed above. The presence of more than a few 

seepage indicators in abundance would be indicative of a seepage wetland. 

OUTLINE OF THE CLASSIFICATION HIERARCHY 

The classification of communities is organized in a nested hierarchy (Table 3). The highest 

levels of the hierarchy are the system (e.g., palustrine vs. estuarine) and the gross physiognomy 

(e.g., forests vs. open). The finer levels utilize ecological characteristics that indicate major 

ecological differences among groups of communities, particularly water source and soil texture. 

These environmental attributes are applied in different combinations to organize communities 

depending on their indicator value within each major group of communities (e.g., peatlands, river 

channel communities, and floodplain forests). 

Table 3. Organization of New Hampshire wetland natural community classification. 

CLASSIFICATION 

LEVEL 

System 

Gross physiognomy 

(coarse structure) 

Environmental 

characteristics: 

(hydrology, soil texture, 

and nutrient regime) 

Fine physiognomy: 

(life forms and functional 

traits of species) 

CATEGORIES 

(1) Palustrine and river channel 

(2) Terrestrial 

(3) Estuarine 

(4) Aquatic 

(1) Forests (>60% tree cover) and woodlands 

(25-60% cover) 

(2) Open (

Wetland Natural Community Descriptions 

New Hampshire Natural Heritage Inventory 


WETLAND NATURAL COMMUNITIES OF NEW HAMPSHIRE 

Open Palustrine and River Channel Systems (non-peatlands) 

Soligenous 

Mineral or Outcrop Substrate 

• Acidic riverside seep (G3G4 S1)..........................................................................................................23 

• Calcareous riverside seep (G2G3 S1).....................................................................................................23 

• Cliff seep (S3S4) ....................................................................................................................................24 

Shallow Organic over Mineral Substrate 

• Undifferentiated seepage marsh (S3S4) .................................................................................................25 

• Alpine herbaceous snowbank (S1) .........................................................................................................26 

• Alpine herbaceous-heath meadow (S1)..................................................................................................26 

Limnogenous 

Outcrop/Cliff 

• Riverside outcrop (G S1S3) ..................................................................................................................26 

Coarse-Medium Mineral Substrates 

Dry-Mesic Dwarf Shrub/Forb Riverside Sand to Cobble/Gravel Barrens......................................................27 

• Riverside Hudsonia sand/gravel barren (G2 S1) ....................................................................................27 

• Dwarf cherry riverside sand-cobble barren (S1S2) ................................................................................28 

• Undifferentiated riverside sand/gravel barren (S3S4) ............................................................................28 

• Undifferentiated dry-mesic high-energy riverbank (SU)........................................................................29 

Mesic-Wet Graminoid-Forb Riverside Sand/Gravel Barrens and Meadows 

• Twisted sedge meadow/barrens (S3S4)..................................................................................................29 

• Big bluestem-hairgrass forb meadow (S3S4) .........................................................................................29 

• Undifferentiated mesic-wet graminoid-forb meadow/barren (S3)..........................................................29 

Mesic-Wet Shrub-Herb Riverside Thickets 

• Speckled alder/bryophyte shrub-herb thicket (S3) .................................................................................30 

• Mixed herb/shrub-liana thicket (S3S4)...................................................................................................30 

• Undifferentiated shrub-herb thickets (S4) ..............................................................................................30 

Fine Mineral Substrates 

Mixed Herb and Shrub Thickets 

• Reed bent-grass-goldenrod-Clematis meadow/shrubland (S3S4) ..........................................................30 

• Alder-dogwood-meadow-sweet-Viburnum riverside shrub thicket (S4)................................................31 

• Meadow-sweet riverside shrub thicket (S3) .........................................................................................32 

Graminoid-Herb Meadow 

• Northern riverside graminoid-herb meadow (S1S3) ..............................................................................32 

Topogenous/Limnogenous 

Low-Energy Streamside, Riverine, and Open-basin Settings 

Shallow Emergent Marshes 

• Tall graminoid emergent marshes (S4)...................................................................................................34 

• Mixed tall graminoid/medium to tall shrub marsh (S4S5) .....................................................................34 

• Northern medium-sedge meadow marsh (S3) ........................................................................................34 

• Oxbow marsh (S3)..................................................................................................................................34 

• Short graminoid-forb emergent marsh/mud flat (S4) .............................................................................35 

Medium-Depth Emergent Marshes 

• Graminoid-aerenchymatous medium-depth emergent marsh (S3S4).....................................................36 

• Open-basin cattail marsh (S4)...............................................................................................................36 

• Riverside cattail marsh (S2S3) .............................................................................................................37 

• Undifferentiated tall graminoid medium-depth emergent marsh (S4)....................................................37 

Deep Emergent Marshes 

• Aerenchymatous/aquatic deep emergent marsh (S4)..............................................................................37 



Shrub Thickets (non-peatland types) 

• Highbush blueberry-winterberry tall shrub thicket (S4).........................................................................38 

• Buttonbush basin swamp (S4) ..............................................................................................................39 

• Oxbow buttonbush swamp (S3)..............................................................................................................39 

• Speckled alder basin/seepage shrub thicket (S3S4)................................................................................39 

Low- to High-Energy Sandy Pond Shore, Closed Sand Plain Basin, and Sand Dune Settings 

Sandy Pond Shore Settings 

• Sweet gale-speckled alder-steeple-bush medium-tall shrub thicket (S3)................................................40 

• Twig-rush sandy turf pond shore (S1) ....................................................................................................41 

• Bulblet umbrella-sedge open sandy pond shore (S2)..............................................................................42 

• Submerged aquatic/rosette stress tolerant sandy pond shore (S1S2) ......................................................42 

Sand Plain Closed-Basin Marsh Settings 

• Dense blueberry-winterberry-mountain holly tall shrub thicket (S4) .....................................................43 

• Robust graminoid/medium shrub/Sphagnum marsh (S3S4)...................................................................43 

• Meadow beauty-slender spike-rush-spurned panic-grass-one-flowered muhly sand plain marsh (S1)..44 

• Three-way sedge-Small’s spike-rush-manna-grass mud flat marsh (S2S3) ...........................................45 

• Blunt & olive-brown spike-rush-floating-leaved aquatic mud flat (S1) .................................................46 

• Sharp-flowered manna-grass shallow peat marsh (S1)...........................................................................47 

• Northern basin marsh (S1)......................................................................................................................47 

Coastal Sand Dune Settings 

• Coastal interdunal marsh/swale (S1) ......................................................................................................48 

Aquatic Bed Communities 

• River rapids (S3).....................................................................................................................................49 

• Yellow pond lily-pickerelweed-pondweed aquatic beds (S4S5) ............................................................50 

Open Peatland Communities 

Mud-bottoms, Open Moss Lawns, and Flarks 

Oligotrophic Types (Very Acidic) 

• Liverwort/horned bladderwort mud-bottom (S3) ...................................................................................52 

• Sphagnum rubellum/small cranberry dwarf heath moss lawn (S3) ........................................................53 

Oligotrophic – Weakly Minerotrophic Types (Acidic) 

• Sphagnum pulchrum/sedge moss lawn (S2S3).......................................................................................54 

• Sphagnum cuspidatum/large cranberry moss lawn (S3).........................................................................54 

• Sphagnum torreyanum/large cranberry/white beak-rush moss lawn (S3) ..............................................55 

Minerotrophic Types (Circumneutral – Calcareous) 

• Circumneutral-calcareous flark (S1).......................................................................................................55 

Dwarf- and Medium-Shrub Bogs and Poor Fens 

Oligotrophic Alpine/Subalpine bogs and Subalpine Heath snowbanks (Very Acidic) 

• Wet alpine/subalpine level and sloping bog (S1) ...................................................................................56 

• Subalpine wooded heath snowbank, slope bog, and bog margin (S1S2)................................................57 

• Subalpine sliding fen (S1) ......................................................................................................................58 

Oligotrophic – Weakly Minerotrophic Mid-Low Elevation Bogs and Poor Shrub Fens (Very Acidic – Acidic) 

• Leather-leaf-sheep laurel/Sphagnum capillifolium dwarf heath shrub bog (S1 and S3) ........................58 

• Leather-leaf-sheep laurel/black spruce dwarf heath shrub bog/very poor fen (S3) ................................59 

Intermediate – Minerotrophic (Circumneutral) Type 

• Northern white cedar circumneutral string (S1)....................................................................................60 

Sedge and Shrub/Graminoid Fens 

Weakly Minerotrophic Types (Acidic) 

• Bog rosemary-sweet gale/bottle-shaped sedge/Sphagnum fallax fen (S3) .............................................61 

• Sweet gale-meadow-sweet/tussock sedge streamside/pond-border fen (S4)..........................................61 

• Water willow/Sphagnum recurvum-S. flexuosum border thicket (S3)...................................................62 

• Montane Pickering’s reed bent-grass/shrub level/sloping fen (S1) ........................................................62 



Intermediate Types (Subneutral) 

• Hairy-fruited sedge/sweet gale-large cranberry sedge fen (S3)..............................................................63 

• Speckled alder/lake sedge-skunk cabbage intermediate fen (S2S3).......................................................63 

Intermediate – Minerotrophic (Mesotrophic) Types (Circumneutral – Calcareous) 

• Calcareous sedge/moss fen (S2).............................................................................................................64 

• Graminoid-forb-sensitive fern seepage marsh (S3) ................................................................................66 

Tall – Medium Shrub Thicket/Sparse Woodlands 

Oligotrophic – Weakly Minerotrophic Types (Very Acidic – Acidic) 

• Highbush blueberry-mountain holly shrub thicket/sparse woodland (S3S4) .........................................67 

Weakly Minerotrophic Montane Tall Shrub Thicket/Sparse Woodlands 

• Montane heath shrub thicket/sparse woodland (S2) ...............................................................................69 

• Montane alder-heath shrub thicket (S1)................................................................................................69 

Weakly Minerotrophic – Intermediate Types (Acidic – Subneutral) 

• Winterberry/cinnamon fern/spruce tall shrub thicket/sparse woodland (S4)..........................................69 

• Winterberry/cinnamon fern/Sphagnum fallax tall-medium shrub thicket (S4) ......................................70 

• Highbush blueberry/sweet gale-meadow-sweet tall-medium shrub thicket (S4)....................................71 

Marshy Peatland-margin Communities 

• Floating marshy peat mat (S3)..............................................................................................................72 

• Marshy moat (S4)...................................................................................................................................72 

Forested Swamps and Floodplain Forests 

Saturated/Seasonally Flooded Basin Swamps 

Muck and Peat Swamps 

• Red maple/Sphagnum saturated basin swamp (S4)................................................................................74 

• Atlantic white cedar-yellow birch/sweet pepperbush swamp (S2).........................................................76 

• Boreal Atlantic white cedar swamp (S1)................................................................................................77 

• Black spruce-larch/heath/Sphagnum basin swamp (G5 S3)...................................................................78 

• Black gum-red maple basin swamp (S1S2)............................................................................................80 

Mineral Soil Swamps 

• Swamp white oak basin swamp (S1)......................................................................................................84 

Seepage Swamps and Mixed-Hydrology Swamps 

Weakly Acidic to Intermediate/Circumneutral Swamp Forests and Woodlands 

• Red maple-black ash/swamp saxifrage seepage swamp (S2) .................................................................84 

• Red maple/lake sedge streamside/seepage swamp (S3) .........................................................................85 

• Circumneutral/basic seepage swamp (S1) ..............................................................................................85 

• Northern hardwood-black ash-conifer seepage swamp (S2) ..................................................................86 

• Northern white cedar-balsam fir seepage swamp (G4 S2) .....................................................................89 

• Boreal acidic northern white cedar swamp (G4 S1) ...............................................................................92 

• Seasonally saturated northern white cedar seepage forest (S2) ..............................................................92 

• Northern white cedar-hemlock-red maple swamp (G4 S2) ....................................................................93 

Weakly Acidic to Acidic Swamp Forests/Woodlands 

• Red maple/sensitive fern-tussock sedge basin/seepage swamp (S2S3)..................................................93 

• Red spruce/cinnamon fern-three seeded sedge/Sphagnum swamp (S3).................................................94 

Forest Seeps 

• Acidic Sphagnum seep (S3S4) ...............................................................................................................98 

• Subneutral forest seep (S3S4).................................................................................................................99 

• Circumneutral hardwood forest seep (S3) ............................................................................................102 

Seasonally Flooded to Seasonally Saturated Swamps 

• Seasonally flooded Atlantic white cedar swamp (S2) ..........................................................................104 

• Seasonally flooded red maple swamp (S4S5).......................................................................................106 

• Seasonally saturated red maple swamp (S3S4) ....................................................................................106 

• Seasonally flooded boreal swamp (SU)................................................................................................106 



Temporarily Flooded/Seasonally Saturated Floodplain and Terrace Forests 

Floodplain Forests of Major Rivers 

Silver Maple Floodplain Forests 

• Silver maple/wood nettle-ostrich fern floodplain forest (S2) ...............................................................109 

• Silver maple/false nettle-wood reed-sedge floodplain forest (S2)........................................................111 

Sugar Maple Floodplain Forests 

• Sugar maple/ironwood/short husk floodplain forest (S1).....................................................................112 

• Sugar maple-silver maple-white ash floodplain forest (S1S2) .............................................................114 

Floodplain and Terrace Forests of Third and Some Fourth-Order Rivers 

Forests on Circumneutral Soils 

• Swamp white oak floodplain forest (S1) ..............................................................................................116 

• Basswood-white ash-black maple floodplain forest (S1) .....................................................................118 

• Rich sugar maple-ash-oak-hickory forest (S1) .....................................................................................119 

Forests on Subneutral to Circumneutral Soils 

• Red maple floodplain forest (S2S3)......................................................................................................120 

• Balsam fir floodplain forest (S2) ..........................................................................................................124 

• Sycamore floodplain forest (S1)...........................................................................................................125 

Forests on Acidic Soils 

• Low hemlock-hardwood/cinnamon fern forest (S4) ...........................................................................126 

Vernal Pools 

• Vernal woodland pool (S3)...................................................................................................................128 

• Vernal floodplain pool (S2)..................................................................................................................128 

Estuarine Systems 

Intertidal Marshes 

• Low salt marsh (S3)..............................................................................................................................129 

• High salt marsh (S3).............................................................................................................................131 

• Brackish marsh (S2S3) .........................................................................................................................137 

• Coastal salt pond marsh (G4 S1) ..........................................................................................................140 

• Low brackish tidal river-bank marsh (S1S2)........................................................................................141 

• High brackish tidal river-bank marsh (S1S2) .......................................................................................142 

Intertidal Flats and Shores 

• Coastal shoreline strand/swale (S2)......................................................................................................144 

• Intertidal rocky shore (S3)....................................................................................................................145 

• Saline/brackish intertidal flat (S3) ........................................................................................................145 

Subtidal Communities 

• Undifferentiated saline/brackish subtidal channel/bay bottom (S3) .....................................................147 

• Tidal creek bottom (S3)........................................................................................................................148 

• Eelgrass bed (S1)..................................................................................................................................148 

• Oyster bed.............................................................................................................................................149 


OPEN PALUSTRINE AND RIVER CHANNEL SYSTEMS (NON-PEATLANDS) 

(OUTCROP, MINERAL, AND MUCK SOIL SUBSTRATES) 

SOLIGENOUS 

The following types are soligenous (with a reliable source of groundwater seepage) or 

soligenous with limnogenous or topogenous influence. 

MINERAL OR OUTCROP SUBSTRATE 

• Acidic riverside seep (G3G4 S1) 

This community occurs on seepy, open bedrock or cobble, sand or silt substrate of flood scoured 

shores of larger New Hampshire rivers where cold seepage generates fen-like conditions. It is 

distinguished from calcareous seeps by the absence of calcareous indicators and from riverside 

outcrops by the presence of acidic, wet-site indicators. Species include Chamaedaphne calyculata 

(leather-leaf), Vaccinium macrocarpon (large cranberry), Agalinis purpurea (purple gerardia), 

Viola lanceolata (lance-leaved violet), Rhododendron canadense (rhodora), Lyonia ligustrina 

(maleberry), Drosera rotundifolia (round-leaved sundew), Carex canescens, Matteuccia 

struthiopteris (ostrich fern), Lysimachia terrestris (swamp candles), Scirpus cyperinus (woolgrass), 

Houstonia caerulea (bluets), Spiraea latifolia (meadow-sweet), Alnus spp., Hypericum spp. 

(St. Johnsworts), mosses, and liverworts. Northern occurrences may have such species as Picea 

mariana (black spruce), Gaultheria hispidula (creeping snowberry), and Ledum groenlandicum 

(Labrador tea). Drier outcrop areas present often have such species as Andropogon scoparium 

(little bluestem), A. gerardii (big blue-stem), Panicum spp., Aster spp., Solidago graminifolia 

(grass-leaved goldenrod), and numerous other graminoids and composites. This community is 

apparently rare in New England; however, further documentation is needed to determine its 

distribution. Northern and southern variation deserves further scrutiny. Good examples occur at 

Lower Falls Seep (Ammonoosuc River) and Garvins Falls (Merrimack River, Concord). 

• Calcareous riverside seep (G2G3 S1) 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: Calcareous riverside seeps occur at river narrows 

of major rivers and below dams (usually at river narrows where riverside seeps were likely natural), 

on outcrops and occasionally on sediments of steep terraces or cobble bars where there is yearround 

influence of groundwater seepage. Emergent and subsurface seepage through silty cracks in 

bedrock, or in cobble, gravel, sand, or silt substrates is evident by the presence of species indicative 

of cold, fen-like, calcareous conditions. Annual flood and ice scour is violent and removes 

competing woody vegetation. Drier, non-seepy or ledge outcrop areas may be interspersed with 

seepy spots. Most seeps of smaller rivers appear to be acidic and/or harbor acid-loving plants. 

SOILS/GEOLOGY/HYDROLOGY: Soils tend to be turfy sands (i.e., sand impregnated with a tightly 

woven fine root mass) wedged in cracks of outcrop, boulders, cobble and bare outcrop. Little to no 

organic horizon accumulates or is at least stripped away each year. Less often seep vegetation can 


e found in unconsolidated sediments of steep river terraces or silty banks. Partial shading from 

trees and shrubs is typical. Calcareous riverside seeps appear to be restricted to areas with 

considerable calcareous bedrock influence or at least mineral enriched groundwater, and pH of 

seepage water ranged from 6.8 to 8.2 in areas sampled. pH of river water was usually close to 7.0. 

Conductivity ranged from 130 to 330 uS, with one reading each of 60 and 420 at different sites. 

CHARACTERISTIC VEGETATION: Dominant plant species tend to vary between examples, but many 

characteristic and rare forbs, grasses, and sedges are typically present, including a variety of 

midwestern prairie species. Characteristic species include Lobelia kalmii (Kalm's lobelia)*, 

Tofieldia glutinosa (false asphodel)*, Parnassia glauca (grass-of-Parnassus)*, Carex garberi 

(Garber's sedge)*, Rhynchospora capillacea (hair-like beak-rush)*, Equisetum variegatum 

(variegated horsetail)*, Senecio pauperculus (dwarf ragwort)*, Mimulus moschatus 

(muskflower)*, Spiranthes lucida (shining lady's tresses)*, Scirpus spp., and Houstonia caerulea 

(bluets). On drier areas Andropogon gerardii (big blue-stem), Schizachyrium scoparium var. 

scoparium (little bluestem), Deschampsia caespitosa (tufted hairgrass), Campanula rotundifolia 

(round-leaved bellflower), Toxicodendron radicans (poison ivy), and Prunus pumila var. depressa 

(sand cherry) may occur. Shrub border areas may include Cornus stolonifera (red osier dogwood), 

Alnus crispa (mountain alder), Spiraea latifolia (meadow-sweet), and Salix spp. (willows). Further 

floristic analysis is needed to better describe included plant associations. Hydroelectric dams are a 

threat to the long-term existence of these communities in New England. 

GOOD EXAMPLES: Limited to the Connecticut River. 

SOURCES: NH Heritage field surveys; Rawinski (1983a). 

• Cliff seep (S3S4) 

Cliff seeps are differentiated from other seeps by their occurrence on steep rock outcrops or 

cliffs. As such, soil accumulation is largely limited to bedrock cracks, small ledges, or thin 

layers on the rock surface. This group of communities is poorly studied, but there is apparent 

variation in species composition that relates to major pH and climate differences. As data are 

presently limited, two broad types are described here. Future research may indicate 

modifications to the scheme presented here. These include: 

1. Acidic/subneutral cliff seeps (alpine, montane/subalpine and Appalachian/southern types), and 

2. Circumneutral/basic cliff seeps (montane/subalpine and Appalachian/southern types). 

Variation in mineral composition of bedrock is frequent and can occur at a small-scale, often 

resulting in localized zones of higher base-cation content (for instance, from weathering and 

deposition of material from calcium-bearing dikes or sills transported through fractures). Thus, 

the pH, nutrient status, and species composition of cliffs may vary considerably even within a 

single ledge. Moss and liverworts are often dominant, though little has been documented on the 

species composition. Some Sphagnum seeps on the brow of cliff faces in the White Mountains 


should be more thoroughly sampled and compared to sliding fens, acidic Sphagnum seeps on 

mineral soil, and acidic fens. 

Acidic/subneutral cliff seeps may contain vascular species including Aster acuminatus 

(whorled aster), Drosera rotundifolia (round-leaved sundew), Viola macloskeyi var. pallens 

(northern white violet), Viola cucullata (blue marsh violet), Viola spp. (violets), Phegopteris 

connectilis (long beech fern), Chrysosplenium americanum (golden saxifrage), Rubus hispidus 

(bristly dewberry), Solidago rugosa (rough goldenrod), Cinna latifolia (drooping woodreed), Rubus 

pubescens (dwarf raspberry), Circaea alpina (small enchanter's nightshade), Platanthera dilatata 

(tall white bog orchid), Carex pensylvanica (Pennsylvanian sedge), Epilobium spp. (willow-herbs), 

Carex scabrata (rough sedge), and Prenanthes altissima (tall white lettuce). Common tree saplings 

may include Tsuga canadensis (hemlock) and Betula alleghaniensis (yellow birch). 

Circumneutral cliff seeps may contain species listed for acidic seeps but are differentiated 

by the presence of circumneutral-indicators. These include Saxifraga virginiensis (early 

saxifrage) and Eupatorium rugosum (white snakeroot), and in northern or subalpine examples 

Trichophorum alpinum (=S. hudsonianus; northern cotton club rush), Scirpus cespitosus (tussock 

bulrush), Cystopteris bulbifera (bulblet bladder fern), Potentilla fruticosa (shrubby cinquefoil; 

Dasiphora fruticosa ssp. floribunda), Calamagrostis lacustris (pond reed bent-grass)*, 

Pinguicula vulgaris (common butterwort)*, Muhlenbergia glomerata (clustered marsh muhly), 

and Senecio robbinsii (Robbins’ ragwort; =Packera schweinitziana). Bryophytes are common 

to abundant. One example in the Connecticut River valley contains the rare moss Thamnobryum 

alleghaniense. 

Alpine cliff seeps contain such species as Salix herbacea (dwarf willow)*, Geum peckii 

(mountain avens)*, Arnica lanceolata (arnica)*, Saxifraga rivularis (alpine brook saxifrage)*, 

and Saxifraga cernua (nodding saxifrage)*. 

Good examples occur at the Flume (Lincoln), Smarts Brook (Thornton; montane acidic type), 

Ice Gulch (Randolph; circumneutral montane type), Connecticut River State Forest 

(circumneutral southern type), west ridge of Mt. Lincoln (Franconia), and Tuckerman’s and 

Huntington Ravines (alpine type). 

SHALLOW ORGANIC OVER MINERAL SUBSTRATE 

Three natural communities are described for this category. A fourth, Graminoid-forbsensitive 

fern seepage marsh has similarities to certain fens, so it is described under Open 

Peatlands - Sedge and Shrub/Graminoid Fens. 

• Undifferentiated seepage marsh (S3S4) 

The undifferentiated type referenced here corresponds to seepage marshes that do not correspond 

well to the graminoid-forb-sensitive fern seepage marsh (described elsewhere, see above). Also 

compare to Alnus incana/Carex lacustris-Symplocarpus intermediate shrub-herb fen. 


Seepage marshes typically occupy small areas of larger wetland complexes along a 

groundwater discharge area at the wetland margin, along first or second order stream drainages, 

at the interface of a drainage with a larger marsh, or other areas where groundwater discharge is 

prominent. They tend to be larger than forest seeps and do not have a significant tree canopy 

influence except along the borders. They appear to be intermediate between fens and marshes, 

although they are poorly documented and are apparently infrequent to rare. Typical marsh plants 

may be common or even dominant in some examples, but seepage marshes can be distinguished 

by the presence of certain seepage indicators or fen species such as Saxifraga pensylvanica 

(swamp saxifrage), Senecio robbinsii (Robbins ragwort), Hydrocotyle americanum (water 

pennywort), Chrysosplenium americanum (golden saxifrage), Carex lacustris (lake sedge), 

Carex prasina (drooping sedge), or Carex scabrata (scabrous sedge). Mosses may be abundant 

but Sphagnum is generally absent. Mosses include Mnium spp. and Philinotis fontana, among 

many others. 

• Alpine herbaceous snowbank (S1) 

Local, late-melting snowpacks allow herbaceous montane lowland plants to persist high into 

the alpine zone (4700-5500 ft.) along with alpine plants. Some are associated with seepage 

zones, which are generally absent from heath snowbanks. Composition varies from herb to herb 

and heath dominated mixes. Characteristic species include Deschampsia flexuosa (common 

hairgrass), Solidago macrophylla (large-leaved goldenrod), Vaccinium cespitosum (dwarf 

bilberry), Clintonia borealis (blue bead lily), Coptis trifolia (goldthread), and Carex brunnescens 

(brownish sedge) along with alpine restricted species absent from lower elevation snowbanks 

(e.g., Carex bigelowii (Bigelow's sedge)). 

• Alpine herbaceous-heath meadow (S1) 

Moist tundra (e.g., near streams or snowbanks) dominated by a diverse mix of forbs, sedges, 

and heath shrubs including Geum peckii (mountain avens)*, Scirpus cespitosus (deer's-hair 

sedge), Polygonum viviparum (viviparous knotweed), Salix uva-ursi (bearberry willow), 

Campanula rotundifolia (harebell), Carex scirpoidea (scirpus-like sedge), and Prenanthes boottii 

(Boott's rattlesnake-root). In New Hampshire, found only in Alpine Garden (5000-5500 ft.). 

LIMNOGENOUS 

OUTCROP/CLIFF 

(TEMPORARILY TO INTERMITTENTLY FLOODED, MODERATE TO HIGH ENERGY RIVERINE SETTINGS) 

• Riverside outcrop (G S1S3) 

This natural community includes open, flood-scoured bedrock exposures along major rivers, 

typically along river-narrows (based on NH Heritage field surveys and Rawinski (1984)). Emergent 

seepage is absent as are the corresponding seepage and wetland plants found in riverside seeps. 


Sedges are often notably lacking compared to seeps. This community may, however, occur in 

conjunction with seep communities on drier rock exposures. This community differs from rock 

outcrop/rocky summit communities by the paucity of lichen and woody species intolerant of flooding, 

and the presence of flood-tolerant species. Plants may be stressed or killed during severe drought 

periods that may be common on middle to higher elevation outcrop areas. 

Characteristic species include Schizachyrium scoparium var. scoparium (little bluestem), 

Andropogon gerardii (big blue-stem), Campanula rotundifolia (round-leaved bellflower), 

Toxicodendron radicans (poison ivy), Aster linariifolius (linear-leaved aster), Arctostaphylos uva-ursi 

(bearberry), Prunus pumila var. depressa (sand cherry), Deschampsia caespitosa (tufted hairgrass), 

Solidago glutinosa var. racemosa (riverbank goldenrod). Northern New Hampshire examples may 

have species such as Populus balsamifera (balsam poplar), Thuja occidentalis (northern white cedar), 

Vaccinium cespitosum (dwarf bilberry), Potentilla tridentata (three-toothed cinquefoil), and Trisetum 

spicatum var. pilosiglume (spiked false oats). Dwarf bilberry and three-toothed cinquefoil are 

otherwise restricted to alpine areas and high elevation outcrops. Exotics are common. 

Many examples are acidic although some are apparently circumneutral. Plants that are 

probably indicative of circumneutral or more enriched conditions may include round-leaved 

bellflower, Senecio pauperculus (dwarf ragwort)*, Astragalus robbinsii var. jesupii (Jesup's milkvetch)*, 

and Allium schoenoprasum var. sibiricum (Siberian chives)*. Much more research is 

needed to determine floristic differences among riverside outcrops and the controlling 

environmental factors. 

Occurrences of significant size are limited to major rivers (Connecticut and Merrimack, 

possibly others). A good example occurs at No-Mans Island (Bath). 

COARSE-MEDIUM MINERAL SUBSTRATES 

(BOULDERS TO SAND, TEMPORARILY FLOODED, MODERATE TO HIGH ENERGY RIVERINE SETTINGS) 

DRY-MESIC DWARF SHRUB/FORB RIVERSIDE SAND TO COBBLE/GRAVEL BARRENS 

• Riverside Hudsonia sand/gravel barren (G2 S1) 

Intermittently flooded sand and gravel bars (Suncook Loamy Fine Sand) of the upper Saco 

River drainage characterized by and distinguished from other sand/gravel bar communities by an 

abundance of Hudsonia tomentosa var. intermedia (hairy hudsonia)* and usually Paronychia 

argyrocoma var. albimontana (silverling)* (based on NH Heritage field surveys and Rawinski 

(1985)). These xeric, oligotrophic alluvial deposits are typically found on point-bars where plant 

association zonation represents a gradient of flood frequency, flood intensity, and sediment size 

and load. Wind and water formed dunes may be present. The lowest most frequently flooded zone 

consists mostly of bare sand, adjacent to shrub thickets with Salix (willow), Spiraea (meadowsweet) 

and Cornus (dogwood), and followed by sand barrens with Hudsonia and silverling. Other 

species typically present include Andropogon scoparium (little bluestem), Danthonia spicata, 

Panicum sp., Lechea intermedia (pinweed), Solidago graminifolia (grass-leaved goldenrod), 

Solidago nemoralis, Apocynum sibiricum (prairie dogbane), Betula populifolia (gray birch), Betula 


papyrifera (white birch), Pinus rigida (pitch pine), P. strobus (white pine) and exotics such as 

Rumex acetosella (field sorrel) and Achillea millefolium (yarrow). In New Hampshire, silverling is 

otherwise only known from mid to high elevation outcrops and cliffs, and Hudsonia from sandy 

beach-strand shores and coastal sand formations. This rare association is otherwise known only 

from ridge top barrens of Panther Knob, West Virginia. A good example occurs at Townline 

Gravel Barrens, North Conway. 

• Dwarf cherry riverside sand-cobble barren (S1S2) 

Prunus pumila riverside sand-cobble barren 

To be described in forthcoming report on classification of open floodplain natural 

communities in New Hampshire (Nichols et al. In press). 

• Undifferentiated riverside sand/gravel barren (S3S4) 

This group corresponds to open sand, gravel and cobble bars in the river channel that are 

subjected to flood and ice scour that are not described elsewhere. These are high-energy 

riverbanks that are typically dry or merely moist for most of the growing season. A variety of 

graminoid and herb species are usually the most abundant vegetation, but mineral substrate 

dominates the ground surface. Medium-height shrubs range from absent to moderate abundance. 

Riverside sand and gravel bars dominated by shrubs or vines are described elsewhere. Variation 

in species composition is probably related to the severity, frequency, and timing of flooding and 

ice scour, substrate texture, and deposition dynamics of the stream channel. Some examples 

have native “prairie species” as well as numerous exotics. Both northern and southern types are 

known; but additional data are needed to determine major floristic differences. Plants that may 

be present in southern New Hampshire examples include Andropogon gerardii (big blue-stem), 

Schizachyrium scoparium (little bluestem), Populus deltoides (eastern cottonwood) Panicum 

virgatum (switch-grass), Toxicodendron radicans (poison ivy), Prunus pumila var. depressa 

(sand cherry), and Apocynum sibiricum (prairie dogbane). The bluestems are often among the 

dominant plants. Other characteristic species that may be present include Cyperus spp. 

(umbrella sedges), Lespedeza capitata (round-headed bush clover), Eragrostis spectabilis 

(tumble-grass), Poa compressa, Panicum spp., Rubus flagellaris (running blackberry), Salix sp., 

and numerous exotic disturbance-colonizers. The rare cobblestone tiger beetle (Cicindela 

marginipennis) occurs in this community along the Connecticut River. Coastal examples are 

present but fairly small and not well documented. 

This community is frequent along certain stretches of the Connecticut and Merrimack Rivers, 

and on other major waterways in the state. The only presently documented coastal examples are 

along the Lamprey River. 


• Undifferentiated dry-mesic high-energy riverbank (SU) 

This is a broadly defined and probably variable complex of communities occupying regularly 

flooded, coarse to medium substrates of high-energy riverbanks that are not described elsewhere. 

Open, dry-mesic habitats of sand/gravel bars with little plant cover and mesic meadows on fine 

alluvium are described elsewhere. Herbs and shrubs may be dense to sparse along a typically 

narrow and continuous zone of rocky shore, or other substrate of consolidated or unconsolidated 

material along the riverbank. This community often occurs in conjunction with undifferentiated 

mesic-wet high energy riverbanks (see below) found lower on the gradient towards the river’s edge. 

The upper portion of high-energy riverbanks is temporarily flooded and ice scoured during 

spring high water and during other peak flood events. The vegetation of this habitat is extremely 

variable, as flood intensity and frequency, moisture, soil type and stability, bedrock type and 

local seed sources are all extremely variable, thereby complicating more detailed classification 

attempts at this time. Shrubs, herbaceous plants, and mosses are all variously important below 

the canopy of riverbank trees. Broad substrate types include compact or loose alluvium, till, 

boulders, and rock outcrops. Both upland and wetland species are characteristic, most of which 

are common in other habitats as well. The transition to lower wet riverbank is often rapid and 

subtle, with no clear boundary between the two, although differences are distinct at the extremes. 

Some upper riverbank habitats are prone to draught. 

MESIC-WET GRAMINOID-FORB RIVERSIDE SAND/GRAVEL BARRENS AND MEADOWS 

• Twisted sedge meadow/barrens (S3S4) 

Carex torta meadow/barrens 



1. Carex torta-Apocynum sibericum-Aster novi-belgii/Salix meadow/barren 

2. Carex torta-Onoclea forb meadow 

• Big bluestem-hairgrass forb meadow (S3S4) 

Andropogon gerardii-Deschampsia forb meadow 



• Undifferentiated mesic-wet graminoid-forb meadow/barren (S3) 

This is a broadly defined and probably variable complex of communities occupying regularly 

flooded, coarse to medium substrates of high-energy riverbanks and shores that are not described 

elsewhere (based on NH Heritage field surveys and Sperduto and Crow (1994). Herbs and 

shrubs may be dense to sparse along a typically narrow and continuous zone of rocky shore, or 

other substrate of consolidated or unconsolidated material along the riverbank. This community 


may occur in conjunction with undifferentiated dry-mesic high energy riverbanks (see above) 

found higher on the gradient towards the upland edge. 

This habitat refers to the lower reaches of riverbanks that are exposed at low water and are 

thus seasonally to semi-permanently flooded, saturated, or intermittently exposed. Substrates 

include outcrops and variable alluvium (sand, silt, gravel, cobble or stones or boulders), although 

they may not be present as well-defined or extensive sand/gravel point bars referred to as 

sand/gravel barrens below. These habitats support a variety of wetland species including 

amphibious plants (able to grow under submersed or emergent conditions), emergent plants, and 

moist site species. Common wetland plants described largely from moist or wet riverbanks that 

lack well-developed marshy margins along the Lamprey River include Lobelia cardinalis 

(Cardinal flower), Ludwigia palustris (water purslane), Onoclea sensibilis (sensitive fern) and 

Boehmeria cylindrica (false nettle). Occasionally Mimulus ringens (monkey flower), Cicuta 

maculata (water hemlock), Osmunda regalis (royal fern), Hypericum boreale (northern St. 

John's-wort), and Verbena hastata (vervain) were also found growing along the river margin. 

MESIC-WET SHRUB-HERB RIVERSIDE THICKETS 

• Speckled alder/bryophyte shrub-herb thicket (S3) 

Alnus incana/bryophyte shrub-herb thicket 


communities in New Hampshire (Nichols et al. In press). Habitat for the rare Listera auriculata 

(auricled twayblade)*. 

• Mixed herb/shrub-liana thicket (S3S4) 



• Undifferentiated shrub-herb thickets (S4) 



FINE MINERAL SUBSTRATES 

(SAND TO SILT, TEMPORARILY TO SEASONALLY FLOODED, LOW TO MODERATE ENERGY RIVERINE SETTINGS) 

MIXED HERB AND SHRUB THICKETS 

• Reed bent-grass-goldenrod-Clematis meadow/shrubland (S3S4) 

Calamagrostis-Solidago-Clematis meadow/shrubland 

This community forms temporarily flooded tall herb, vine, and shrub dominated thickets on 

fine alluvial substrates (fine sand or silt) along major and minor rivers and major streams. From 

an elevation perspective, it occurs between sand and gravel bars and floodplain forest. The 


current description for this community will be revised to reflect more recent data in a 

forthcoming report on classification of open floodplain natural communities in New Hampshire 

(Nichols et al. In press). 

Frequent or abundant species include Calamagrostis canadensis (blue-joint), Onoclea 

sensibilis (sensitive fern), Clematis virginiana (virgin's bower), Solidago rugosa (rough 

goldenrod), Solidago gigantea (smooth goldenrod), Rubus occidentalis (western black 

raspberry), Apios americana (groundnut), Eupatorium maculatum (spotted Joe-pye-weed), and 

Panicum clandestinum (deertongue). Occasional species include Euthamia graminifolia (grassleaved 

goldenrod), Muhlenbergia mexicana (Mexican muhly), Agrostis hyemalis (ticklegrass), 

Bromus latiglumis (riverbank brome grass), Elymus riparius (riverbank wild rye), Lysimachia 

terrestris (swamp candles), Toxicodendron radicans (poison ivy), and various sedges in the 

Ovales group such as Carex scoparia (broom sedge), Carex projecta (beaded broom sedge), and 

Carex tribuloides (blunt broom sedge). Non-native species may include Agropron repens 

(witch-grass) and Poa palustris (Kentucky bluegrass). Tall shrubs (e.g., Alnus incana var. 

americana (speckled alder))are generally not dominant or only locally abundant. Recruitment 

may be restricted by flooding and browsing. Medium height shrubs such as Spiraea latifolia 

(eastern meadow-sweet), Spiraea tomentosa (steeplebush) and Cornus spp. (dogwoods) are 

occasional or locally abundant. In more mesic low areas, clones of Scirpus expansus (expansive 

bulrush) are known to occur. 

• Alder-dogwood-meadow-sweet-Viburnum riverside shrub thicket (S4) 

Alnus-Cornus-Spiraea-Viburnum riverside shrub thicket 

This is a broadly defined community (group of communities) characterized by shrub thickets 

on hydric or non-hydric, moist mineral soils(gravel, sand, or silty soils) that are flooded on a 

regular basis. Higher-energy examples on gravel or cobble bars (e.g., Alnus incana/bryophyte 

shrub-herb thicket) are apparently distinct from medium-energy examples on finer sediments. It 

is typically dominated by alders (Alnus rugosa (speckled alder), A. serrulata (common alder)) 

and numerous other shrubs such as Cornus amomum (silky dogwood), Cornus stolonifera (red 

osier dogwood), Salix spp. (willows), Vitis spp. (grapes), Clethra alnifolia (sweet 

pepperbush)(along the coast), Viburnum lentago (nannyberry), Viburnum recognitum 

(arrowwood), and Viburnum cassinoides (witherod). A broad diversity of herbs may also be 

present. This community may occur as broad floodplain thickets along major rivers or as narrow 

zones along large streams and rivers. More data are needed to determine successional trends and 

environmental factors that control variation in species composition. 

Some examples are dominated by one species (e.g., Cornus sericea (red osier dogwood)) and 

warrant consideration as their own community. This community will be described in more detail 

in forthcoming open floodplain report (Nichols et al. In press). 


• Meadow-sweet riverside shrub thicket (S3) 

Spiraea alba riverside shrub thicket 

Spiraea alba var. latifolia (eastern meadow-sweet) dominated shrub thickets along major 

streams and minor rivers. Documented from the Suncook, Soucook, Big, Swift & Blackwater 

rivers. To be described in forthcoming report on classification of open floodplain natural 


GRAMINOID-HERB MEADOW 

• Northern riverside graminoid-herb meadow (S1S3) 

This community occurs along several major streams or minor rivers north of the White 

Mountains and is apparently distinct from other graminoid-herb meadows elsewhere in the state. 

It is characterized by graminoid or graminoid and herb dominated vegetation on intermittently 

flooded silt or fine, sandy alluvial soils of moderate-energy environments. It appears to occur at 

slightly higher elevations than adjacent sand and gravel barrens but lower than adjacent dense 

shrub thickets. Species composition includes both wetland and moist-meadow species generally 

less than 1-1.5 m in height. Non-Sphagnum mosses may be abundant. Topography may 

undulate slightly due to the presence of abandoned, intertwining stream channels. 

Some species of the northern type include Bromus ciliatus (fringed brome-grass), Euthamia 

graminifolia (grass-leaved goldenrod), Carex scoparia (broom sedge), Carex debilis (Rudge's 

sedge), Carex stricta (tussock sedge), Carex folliculata (follicled sedge), Potentilla norvegica 

(cinquefoil), Muhlenbergia mexicana (Mexican muhly), Juncus effusus var. solutus (soft rush), 

Calamagrostis stricta var. inexpansa (neglected reed bent-grass)*, Calamagrostis spp. (bentgrass), 

Ribes spp., and moss spp. Medium height shrubs such as Spiraea latifolia (eastern 

meadow-sweet) or Spiraea tomentosa (steeplebush) may be present or locally abundant. 

Comparisons with other floodplain communities are underway (forthcoming in Nichols et al. 

In press). 

TOPOGENOUS/LIMNOGENOUS 

The following communities occur from limnogenous stream, river and lake shore settings to 

topogenous or topogenous/limnogenous open- or closed-basin settings. 

LOW ENERGY STREAMSIDE, RIVERINE, AND OPEN-BASIN SETTINGS 

(FINE MINERAL TO ORGANIC SUBSTRATES (SAND, MUCK, OR SHALLOW MUCK OVER SAND OR SILT), 

SEASONALLY TO SEMI-PERMANENTLY FLOODED) 

SHALLOW EMERGENT MARSHES 

This is a broad category of communities characterized by permanently saturated to seasonally 

flooded mineral, muck, or shallow fibrous peat soils dominated by grasses and sedges 

(graminoids) or mixes of graminoids, herbs, and medium-height shrubs between 0.5-1.5 m tall. 


These marshes are usually flooded by one to several feet during spring high-water but have 

considerably lower water levels by mid to late summer. Dominance by rhizomatous, clonal 

species is common in shallow and deep emergent marshes, and what species prevail at a site is 

likely controlled by some combination of hydrologic regime and seed or other propagule 

availability. A very high diversity of species has been documented from marshes in general. 

Species richness for a 400 square meter area typically exceeds 30 (-40+) species, even when one 

or a few species accounts for over 50% of the cover (NH Heritage data). 

Typical marsh plants here include Calamagrostis canadensis (blue-joint), Glyceria 

canadensis (rattlesnake-grass), Leersia virginica and L. oryzoides (cutgrass), Phalaris 

arundinacea (reed canary grass), Dulichium arundinaceum (three-way sedge), Carex stricta 

(tussock sedge), Carex lacustris (lake sedge), Scirpus cyperinus (wool-grass), Eupatorium 

dubium (Joe-pie weed), Eupatorium maculatum (spotted Joe-pie-weed), Iris versicolor (blue 

flag), Juncus canadensis (Canada rush), and Thalictrum pubescens (tall meadow rue). Shallow 

emergent marshes may be successional to scrub-shrub swamps and ultimately forested swamps 

over the coarse of decades, or may revert to deep emergent or aquatic bed marshes with 

submergence by damming of the drainage. 

The rare Scirpus ancistrochaetus (northeastern bulrush)* (federally endangered) occurs in 

shallow to somewhat deep emergent marshes. This species does not appear in the common 

botanical manuals, but is closest to Scirpus atrovirens in character. The primary gross difference 

is that the peduncles (fruiting-head stalks) are mostly drooping rather than ascending (bristle 

barbs are also different). Other potential rare species include Mikania scandens (climbing 

hempweed)*, Campanula uliginosa (marsh bellflower)*, Lysimachia thyrsiflora (tufted 

loosestrife)*, Iris prismatica (slender blue flag)*, Carex trichocarpa (hairy-fruited sedge)*, and 

Bidens laevis (smooth bidens)*. Bidens discoidea (small beggars tick)* is no longer considered 

rare and will be delisted due to recent discovery of numerous populations in the state. 

In many cases, shallow emergent marshes are rather mixed in composition and may not fit a 

particular dominance type, or are transitional to shrub thickets. In other circumstances, one or two 

species clearly dominate. Numerous associations or dominance types can be observed, which may 

deserve distinction as community types with an expanded sampling and understanding of 

hydrologic-vegetation dynamics. Presently, we recognize several broad groups of communities 

based on dominant life-forms, some of which have specific communities (associations) defined 

within the groups. More data are needed on the correlation of marsh associations with flood 

regimes, successional stages, seed bank phenomena, and climatic influences (e.g., northern, 

southern, and coastal marshes). The following are some of the more common expressions. 

Two similar natural communities are described elsewhere in this classification. 

Undifferentiated seepage marsh is under soligenous communities in Open Palustrine and River 

Channel Systems – Soligenous. Graminoid-forb-sensitive fern seepage marsh is described in 

Open Peatlands – Sedge and Shrub/Graminoid Fens. 


• Tall graminoid emergent marshes (S4) 

This group of shallow emergent marshes are dominated by tall “matrix” forming graminoids. 

Dominant species are maintained vegetatively through the development of dense tussocks or via 

lateral spread (clonal or spreading from lose tussocks). A broad diversity of other herbs is often 

present, but much of the cover and biomass is contributed by a few species. 

1. Reed-grass meadow: a very common association dominated by Calamagrostis canadensis 

(blue-joint). These “meadows” are often inundated for shorter periods or do not sustain 

water as close to the surface for as long compared to other shallow emergent marshes. 

2. Tussock sedge meadow: dominated by the ubiquitous Carex stricta (tussock sedge). 

3. Bulrush meadow: marshes dominated by bulrushes, most commonly Scirpus cyperinus 

(wool-grass). 

4. Reed canary grass meadow: Phalaris arundinacea (reed canary grass) is dominant in 

this type. 

• Mixed tall graminoid/medium to tall shrub marsh (S4S5) 

This group of communities is similar to the above community group (tall graminoid 

emergent marshes) but contains a substantial component of medium-height shrubs (0.5-1.5 m). 

This is a very common “scrub-shrub”/emergent marsh type that occurs throughout the state. 

Many examples may be successional between marsh and shrub thicket or swamp, but shrubs 

contribute less than 60% cover overall. Species may include a mixture of tall graminoids such as 

blue-joint, tussock sedge, other tall grasses and sedges, cinnamon and royal ferns, Spiraea 

latifolia (meadow-sweet), and Myrica gale (sweet gale). Tall shrubs may include Vaccinium 

corymbosum (highbush blueberry), Ilex verticillata (winterberry), Alnus incana var. americana 

(speckled alder), Viburnum nudum var. cassinoides (witherod), and Salix spp. (willows). This 

community is transitional to streamside poor fens that have a greater abundance of Sphagnum, 

leather-leaf, sweet gale, and “peatland” sedges such as Carex utriculata (bottle-shaped sedge) 

and Carex lasiocarpa var. americana (hairy-fruited sedge). 

• Northern medium-sedge meadow marsh (S3) 

This community is dominated by medium sized sedges (0.3-0.6 m (1-2 ft.) high) such as 

Carex echinata (prickly sedge) and herbs and occur in old, abandoned, “filled-in” beaver 

marshes in the northern part of the state (including the White Mountains). This type is similar or 

transitional to some northern graminoid fens on peat soils. More detailed sampling is warranted. 

• Oxbow marsh (S3) 

Marshes associated with oxbow formations on floodplain terraces are influenced by the flood 

regime of the river itself and modified by the length of inundation and saturation, and the amount 


of time since last flooded. Although these oxbow marshes and oxbow ponds have many of the 

same common wetland plants that occupy shallow and deep emergent marshes and aquatic beds 

in non-river floodplain situations, they have a different and distinct hydrologic "signature" and 

occur in a complex mosaic of plant communities associated with different flood regimes of 

terraces and oxbow channels. In this respect they are significant and distinct ecological variants 

of emergent and aquatic bed communities described elsewhere. A number of these oxbow 

marshes are, to one degree or another, naturally isolated from the present river channel during 

most of the year, but are flooded during spring and other high runoff events. In a broad, 

functional sense, they are vernal pools and have certain similarities to basin marshes, a type of 

vernal wetland system corresponding to isolated, fish-less, vernally flooded basins primarily 

found in sand and gravel outwash terrain that supports open marsh vegetation. Small, forested 

basins under tree canopies with extensive marsh vegetation development are discussed under 

floodplain vernal pools. Carex vesicaria (inflated sedge), Carex lupulina (hop sedge), Leersia 

oryzoides (cutgrass), and Sagittaria latifolia (arrowhead) are common species that may be found 

in shallow emergent oxbow marshes. 

• Short graminoid-forb emergent marsh/mud flat (S4) 

This community or group of communities consists of short (

(lesser bur reed), Peltandra virginica (arrow arum), Pontederia cordata (pickerelweed), and 

Sagittaria spp. (arrowheads). 

Some rare species that may be found in deep emergent marshes include Sparganium 

eurycarpum (giant bur-reed)*, Sparganium androcladum (branching bur-reed)*, Lysimachia 

thyrsiflora (tufted loosestrife)*, and Megalodonta beckii (water marigold)*. 

A variety of wetland birds frequent these marshes including red-winged blackbird (Agelaius 

phoeniceus), pied-billed grebe (Podilymbus podiceps)*, Virginia rail (Rallus limicola)*, marsh 

wren (Cistothorus palustris), and various waterfowl. 

• Graminoid-aerenchymatous medium-depth emergent marsh (S3S4) 

This emergent marsh is dominated by a mix of emergent graminoid and other herbaceous 

aerenchymatous (spongy tissue) species, such as Sparganium americanum (lesser bur-reed), 

Sagittaria latifolia (common arrowhead), Pontederia cordata (pickerel-weed), Eleocharis smallii 

(Small's spike-rush), Polygonum hydropiperoides (mild water pepper), Scirpus tabernaemontanii 

(softstem bulrush), Scirpus pungens (three-square rush), and Typha latifolia (common cattail). 

Marshes dominated almost entirely by tall aerenchymatous graminoids are considered separately. 

• Open-basin cattail marsh (S4) 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: Typha latifolia (common cat-tail) and/or Typha 

angustifolia (narrow-leaved cat-tail) dominated depressions are generally found in seasonally to 

semi-permanently flooded basins with saturated soils in areas where water levels have drawn 

down. Dead thatch from the previous year’s growth can form a thick ground cover in welldeveloped 

clonal stands. Cat-tail marshes on mucky soil in protected depressions/margins of 

lakes, ponds, and slow moving streams are also considered here. 

SOILS/GEOLOGY/HYDROLOGY: Soils may be mucky organic or mineral with a high muck content. 

Standing water typically is seasonal to semi-permanent with exposed soils otherwise saturated or 

with the water table near the surface. 

CHARACTERISTIC VEGETATION: Typha latifolia (common cat-tail) and/or Typha angustifolia 

(narrow-leaved cat-tail) may dominate and exclude nearly all other species or may codominate 

with other herbs and shrubs. Typha x glauca (glaucous cat-tail; Typha angustifolia x Typha 

latifolia) can locally dominate as well. Associates may include Carex stricta (tussock sedge), 

Scirpus cyperinus (woolly bulrush), Sparganium americanum (lesser bur-reed), Glyceria spp. 

(manna-grass), Calamagrostis canadensis (blue-joint), Phragmites australis (common reed), 

Lythrum salicaria (purple loosestrife), Lemna minor (lesser duckweed), Lycopus uniflorus 

(common water horehound), Lysimachia terrestris (swamp candles), Acer rubrum (red maple) 

seedlings and saplings, and several species of shrubs including Spiraea alba var. latifolia 

(eastern meadow-sweet), Ilex verticillata (winterberry), Vaccinium corymbosum (highbush 


lueberry), Viburnum dentatum var. lucidum (northern arrow-wood), and Lyonia ligustrina 

(male-berry). 

CHARACTERISTIC BIRDS: Birds that breed in cat-tail marshes include American bittern, least 

bittern, sora, Virginia rail, marsh wren, swamp sparrow, red-winged blackbird, common 

moorhen, and several species of waterfowl. 

COMMENTS: Some cat-tail marshes immediately adjacent to rivers and lakes likely occur on 

alluvial soils and support a somewhat different array of associated species (see riverside/lakeside 

cat-tail marsh). Typha angustifolia (narrow-leaved cat-tail) may dominate marshes in brackish 

settings in basins adjacent to brackish rivers (see Typha angustifolia brackish marsh), in small 

depressions along the upper edge of low graminoid brackish marshes (see Typha angustifolia 

panne), and within the zone occurring between mean sea level and mean high tide along brackish 

tidal river- and stream-banks (see low brackish tidal river-bank marsh). 

GOOD EXAMPLES: Crommet Creek, Durham 

SOURCES: NH Heritage field surveys. 

• Riverside cattail marsh (S2S3) 



• Undifferentiated tall graminoid medium-depth emergent marsh (S4) 


communities in New Hampshire (Nichols et al. In press). Characteristic species may include 

Scirpus tabernaemontanii (softstem bulrush), Scirpus pungens (three-square rush), Scirpus 

subterminalis (water bulrush), Typha latifolia (common cattail), and Juncus militaris (bayonet 

rush). 

DEEP EMERGENT MARSHES 

• Aerenchymatous/aquatic deep emergent marsh (S4) 

This community contains a mixture of aerenchymatous perennials (e.g., Sparganium 

americanum (lesser bur-reed) and Pontederia cordata (pickerel-weed)), and a moderate 

abundance of floating-leaved or floating-stemmed aquatics such as Nymphaea odorata (white 

water-lily), Nuphar variegata (yellow pond-lily), Lemna spp. (duckweed), Eleocharis smallii 

(Small's spike-rush), Glyceria borealis (northern floating manna-grass), Puccinellia pallida (pale 

manna-grass), and Polygonum hydropiperoides (mild water pepper). Communities dominated 

entirely by floating or submersed aquatics are considered aquatic bed types. 


SHRUB THICKETS (NON-PEATLAND TYPES) 

• Highbush blueberry-winterberry tall shrub thicket (S4) 

Vaccinium corymbosum-Ilex verticillata tall shrub thicket 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This is a seasonally flooded tall shrub 

community found in small open basins, closed sand plain basins, and seasonally flooded zones 

within larger wetlands. Vaccinium corymbosum (highbush blueberry) and Ilex verticillata 

(winterberry) are dominant shrubs. It is found around the upland margin of nearly all closedbasin 

marshes on sand plains. 

SOILS/GEOLOGY/HYDROLOGY: This basin shrub swamp is found on seasonally flooded mineral 

soils that vary in organic content. In some settings, leaf litter covers the basin floor and 

bryophytes and herbs are in low number. This natural community may grade into tall shrub fens 

toward the organic end of the soil gradient. 

CHARACTERISTIC VEGETATION: Dominant shrubs include Ilex verticillata (winterberry) and/or 

Vaccinium corymbosum (highbush blueberry). Seedling and sapling sized Acer rubrum (red 

maple) are often present. Herbs are typically scarce and may include Osmunda cinnamomea 

(cinnamon fern), Osmunda regalis var. spectabilis (royal fern), Thelypteris palustris var. 

pubescens (marsh fern), Lycopus uniflorus (common water horehound), and few others. 

Somewhat more minerotrophic examples may contain Salix spp. (willows), Alnus spp. (alders), 

Viburnum nudum var. cassinoides (witherod), and Cephalanthus occidentalis (buttonbush) in 

low to moderate abundance (never dominant). Two variants are presently recognized: 

1. Typic variant: As described above. 

2. Vaccinium-Ilex-Nemopanthus tall shrub thicket: This variant occurs in more nutrient 

poor settings such as around the margins of sand plain marshes in closed-basins. Lyonia 

ligustrina (male-berry), Chamaedaphne calyculata (leather-leaf), Nemopanthus 

mucronatus (mountain holly), Aronia arbutifolia (red chokeberry), Aronia melanocarpa 

(black chokeberry), and Rhododendron canadense (rhodora) are characteristic of this 

variant. 

COMMENTS: This is a common, widespread, but broadly defined shrub swamp community found 

in open- and closed basin settings. Cephalanthus occidentalis (buttonbush) may be present in 

wetter examples but dominance by buttonbush indicates one of the buttonbush communities 

(seasonally to semi-permanently flooded). The Vaccinium corymbosum-Ilex verticillata basin 

shrub swamp has some floristic similarities to Vaccinium corymbosum-Nemopanthus shrub 

thicket/sparse woodland fens but lacks the deep peat soil, abundant peat mosses, prominent 

medium-height heath shrub layer, and other peatland indicators of this community such as Picea 

mariana (black spruce) and Sarracenia purpurea (pitcher-plant). 

GOOD EXAMPLES: Typic variant: Army Corps of Engineers’ Hopkinton-Everett Lakes property 

(Weare); Grassy Pond (Litchfield). 



• Buttonbush basin swamp (S4) 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: Generally occur in small basins dominated by 

Cephalanthus occidentalis (buttonbush) with standing water present for most or all of the growing 

season. Exposed soil is periodically required for buttonbush regeneration. Buttonbush can also be 

found with other shrubs and herbs along lake and pond margins and slow-moving streams. 

SOILS/GEOLOGY/HYDROLOGY: Basins are typically with well decomposed organic soils, perched 

water tables, and seasonally to semi-permanently flooded hydrology. 

CHARACTERISTIC VEGETATION: Cephalanthus occidentalis (buttonbush) typically dominates 

with a moderate to dense cover. Other species present may include Acer rubrum (red maple), 

Ulmus americana (American elm), Vaccinium corymbosum (highbush blueberry), Alnus incana 

var. americana (speckled alder), Ilex verticillata (winterberry), Rosa palustris (swamp rose), 

Chamaedaphne calyculata (leather-leaf), Kalmia angustifolia (sheep laurel), Viburnum dentatum 

var. lucidum (northern arrow-wood), Thelypteris palustris var. pubescens (marsh fern), Osmunda 

regalis var. spectabilis (royal fern), Osmunda cinnamomea (cinnamon fern), Lycopus uniflorus 

(common water horehound), and Lysimachia terrestris (swamp candles). The persistence of 

standing water throughout much of the growing season limits shrub and herb diversity. Many of 

the shrubs mentioned above may occur with greater cover on drier basin margins or other 

relatively higher ground in the wetland. 

CHARACTERISTIC BIRDS: These wetlands provide brood cover for wood ducks. 

DISTRIBUTION: Widespread in the state but apparently most abundant in central and southern 

New Hampshire. 

COMMENTS: Oxbow buttonbush thickets, a related natural community type, occur on alluvial 

soils in oxbow depressions periodically inundated by riverbank overflow. 

GOOD EXAMPLES: Stratham Hill Park, Stratham 


• Oxbow buttonbush swamp (S3) 



• Speckled alder basin/seepage shrub thicket (S3S4) 

Alnus incana basin/seepage shrub thicket 

This community is dominated by Alnus incana var. americana (speckled alder) and various 

other shrub associates. This is a “boggy alder swamp” that occurs in lower-energy settings than 

alder dominated communities along rivers, in more stagnant settings than Alnus incana/Carex 

lacustris-Symplocarpus intermediate shrub-herb fens. It occurs in open headwater basins and 

along small low-energy streams (e.g. first and second order streams). Muck, peat or mucky peat 


soils are typical. It has fewer heath shrubs (e.g., Rhododendron canadense (rhodora) and Ledum 

groenlandicum (Labrador-tea)) than Montane alder-heath shrub thicket communities described 

from the White Mountains. 

Characteristic shrubs include dominance by speckled alder and lower abundance of such 

shrubs as Cornus sericea (red osier dogwood), Nemopanthus mucronatus (mountain holly), 

Lonicera villosa (villous honeysuckle), Spiraea alba var. latifolia (eastern meadow-sweet), 

Spiraea tomentosa (steeple-bush), Viburnum nudum var. cassinoides (witherod), Ribes triste 

(swamp red currant), and Ribes glandulosum (skunk currant). Herbs and dwarf shrubs are 

common including Carex trisperma var. trisperma (three-seeded sedge), Dryopteris cristata 

(crested wood fern), Dryopteris carthusiana (spinulose wood fern), Smilacina trifolia (threeleaved 

false Solomon's seal), Rubus pubescens (dwarf raspberry), Carex canescens (silvery 

sedge), Carex echinata (prickly sedge), Gymnocarpium dryopteris (oak fern), and Viola spp. 

(violets). Trees generally contribute less than 25% cover and may include Picea mariana (black 

spruce), Abies balsamea (balsam fir), Thuja occidentalis (northern white cedar), and Betula 

populifolia (gray birch). 

LOW TO HIGH ENERGY SANDY POND SHORE, CLOSED SAND PLAIN BASIN, AND SAND DUNE SETTINGS 

(SEASONALLY TO PERMANENTLY FLOODED FINE MINERAL TO ORGANIC SUBSTRATES (SAND, MUCK, AND 

SHALLOW MUCK OVER SAND OR SILT)) 

The following communities occur in sand plain settings (pond shores, closed-basins, and 

interdunal swales). They are distinguished from typical limnogenous wetlands on the basis of 

their unique geomorphic settings, floristic composition, and more broadly fluctuating water 

levels. Vertical water fluctuations (precipitation, evapotranspiration, groundwater fluctuations, 

and limited topographic runoff inputs) dominate the hydrology in closed-basin marshes and 

interdunal swales (e.g., no limnogenous influence). 

SANDY POND SHORE SETTINGS 

• Sweet gale-speckled alder-steeple-bush medium-tall shrub thicket (S3) 

Myrica gale-Alnus incana-Spiraea tomentosa medium-tall shrub thicket 

This temporarily flooded shrub community usually formed a narrow zone at the upland edge 

of pond shores or along the side and top of sandy ice-berms formed on large lakes. It was 

characterized by a mixture of tall and medium shrubs, with lesser amounts of dwarf shrubs and 

herbs. The composition was more diverse than that of dense Vaccinium-Ilex-Nemopanthus tall 

shrub thicket. Diagnostic species occurring with higher frequency and/or greater abundance that 

are absent or infrequent in dense Vaccinium-Ilex-Nemopanthus tall shrub thicket included 

Myrica gale (sweet gale), Alnus incana var. americana (speckled alder), Alnus serrulata (smooth 

alder), Spiraea tomentosa (steeple-bush), Osmunda regalis var. spectabilis (royal fern), 

Viburnum nudum var. cassinoides (witherod), Viburnum dentatum var. lucidum (northern arrowwood), 

and Vaccinium macrocarpon (large cranberry). Other less frequent species that were 


largely limited to this community included Panicum virgatum (switch-grass), Solidago rugosa 

(rough goldenrod), Onoclea sensibilis (sensitive fern), Aster racemosus (small headed white 

aster), Carex stricta var. strictior (small-tussock sedge), Euthamia graminifolia (grass-leaved 

goldenrod), and Carex scoparia (broom sedge). Some of these less frequent species were also 

found in the adjacent (lower) zone occupied by Cladium mariscoides sandy turf pond shore. 

SOILS: Variable soils of sand or sand and gravel, inter-bedded sand and peat turf, or sandy muck 

formed on open pond shore beach ridge or upland edge. Shallow O e horizons (0-13 cm), 

variable A horizons (0-55 cm), with sand and gravel deposits to over 1 m. A single location 

included in this type had over 125 cm of peat at the surface. 

• Twig-rush sandy turf pond shore (S1) 

Cladium mariscoides sandy turf pond shore 

This community occurred on sandy organic turf mats between open water or sand beach and 

shrub communities on sandy shores of large lakes (e.g., Ossipee Lake and Lake Massasecum). 

Wave and ice action were prominent disturbance forces, but less severe than in Cyperus dentatus 

open sandy pond shore and submerged aquatic/rosette stress tolerant sandy pond shore which 

were lower on the shoreline and had much lower percent cover of vegetation. Soil cores of interbedded 

sand, muck, and peat >1.2 m in depth attest to the dynamic nature of these pond shore 

communities on a time scale of decades to centuries. This community was similar to Rhexia 

virginica-Eleocharis tenuis-Panicum spretum-Muhlenbergia uniflora sand plain marsh, but 

contained more robust, rhizomatous, stress tolerant graminoids, a sparse Sphagnum presence, 

and was much more diverse compositionally and structurally. Numerous species of coastal plain 

distribution were found in this community. Cladium mariscoides (twig-rush) was the dominant 

stress tolerant matrix species. Other characteristic species include Euthamia graminifolia (grassleaved 

goldenrod), the state-rare Euthamia tenuifolia (fine grass-leaved goldenrod)*, Carex 

stricta var. strictior (small-tussock sedge) (rhizomatous form), Carex lasiocarpa var. americana 

(hairy-fruited sedge), Calamagrostis canadensis (blue-joint), and Vaccinium macrocarpon (large 

cranberry). Frequent or constant species found in low abundance included Eleocharis tenuis 

(slender spike-rush), Viola lanceolata (lance-leaved violet), Cyperus dentatus (bulblet umbrellasedge), 

Sagittaria latifolia (common arrowhead), Spiraea tomentosa (steeple-bush), Myrica gale 

(sweet gale), Scirpus pungens (three-square rush), Panicum virgatum (switch-grass), Galium 

tinctorium (Clayton's bedstraw), Bidens frondosa (common beggar-ticks), Muhlenbergia uniflora 

(one-flowered muhly), Glyceria canadensis (rattlesnake manna-grass), Dulichium arundinaceum 

(three-way sedge), and Lycopus uniflorus (common water horehound). Lycopodium inundatum 

var. bigelovii (slender bog clubmoss)* and Proserpinaca pectinata (mermaid-weed)* were two 

rare species known from this community but not observed recently along the shores of Ossipee 

Lake. The globally rare Sclerolepis uniflora (sclerolepis)* spilled over into this community from 

deeper water habitats along Lake Massasecum. 

Soils are shallow sandy peat mats alternating with sand layers. Sand dominated below 50 cm 

or in several cores interbedded with organic layers to over 1 m depth. 


• Bulblet umbrella-sedge open sandy pond shore (S2) 

Cyperus dentatus open sandy pond shore 

This natural community consisted of sparsely vegetated lower sandy shores of medium to 

large lakes and ponds subjected to regular wave and ice disturbance and with little to no organic 

matter accumulation. This community was often interspersed discontinuously along unvegetated 

sand beach. With several species of coastal plain distribution, it was similar to Rhexia virginica- 

Eleocharis tenuis-Panicum spretum-Muhlenbergia uniflora sand plain marsh and Cladium 

mariscoides sandy turf pond shore, but had a much lower total percent cover than either, a 

greater prominence of ruderals, and lacked the robust graminoids of Cladium mariscoides sandy 

turf pond shore. Short clumped graminoids, and rhizomatous forbs and graminoids, dominated 

along with numerous native ruderals. Cyperus dentatus (bulblet umbrella-sedge), Viola 

lanceolata (lance-leaved violet), Juncus pelocarpus (mud rush) (rhizomatous), and Bidens 

frondosa (common beggar-ticks) were nearly constant and varied from low to moderate 

abundance. Other frequent species included Panicum spp. (seven species; annuals and 

perennials), Agrostis hyemalis var. scabra (rough ticklegrass), Gratiola aurea (golden-pert), 

Aster racemosus (small headed white aster), Carex scoparia (broom sedge), Eleocharis tenuis 

(slender spike-rush), Euthamia tenuifolia (fine grass-leaved goldenrod)*, Euthamia graminifolia 

(grass-leaved goldenrod), Triadenum virginicum (marsh St. John's-wort), Eriocaulon aquaticum 

(pipewort), and such annuals as Agalinis purpurea var. parviflora (small-flowered gerardia), 

Bidens discoidea (small bidens), Erechtites hieracifolia (fireweed), and on wetter or less exposed 

sections, sometimes Eleocharis acicularis (least spikerush). This community dominated pond 

shore communities on lakes used for water supply storage that had artificially elevated water 

levels (e.g., Lake Massabesic, Manchester). Such lakes may once have supported Cladium 

mariscoides sandy turf pond shores. 

• Submerged aquatic/rosette stress tolerant sandy pond shore (S1S2) 

This natural community occurred in shallow water environments of sandy pond shores 

characterized by a permanently inundated to intermittently exposed flood regime and regular 

wave and ice disturbance. Most examples were characterized by a very low percent cover of 

aquatic rosette-stress tolerant species (including “Isoetids”) and various floating and submersed 

species and submersed forms of normally emergent vegetation. Several examples occurred in 

protected coves or interior pools on Cladium mariscoides sandy turf pond shore mats (Cladium 

mariscoides pond shores) and had a much higher percent cover of vegetation, particularly of 

floating leaved aquatics more sensitive to wave disturbance along exposed shores. 

Two discernable variants were recognized, although some overlap was evident: 

1. Potamogeton-Pontederia pond shore variant: This subtype was characterized primarily 

by floating leaved and aerenchymatous aquatics including Potamogeton epihydrus 

(surface pondweed), Potamogeton natans (floating pondweed), Pontederia cordata 

(pickerel-weed), and Sparganium americanum (lesser bur-reed). Cover varied from very 


low to moderately high in coves. One of these pond shores supported New Hampshire’s 

only population of Sclerolepis uniflora (sclerolepis)* (n=5). 

2. Rosette stress tolerant Isoetid pond shore variant: This type had a lower frequency 

and abundance of floating-leaved aquatics and much higher frequency and abundance of 

rosette stress tolerant “Isoetid” species. The community is only intermittently exposed, 

typically as a narrow band at or near the water level line, with all or a portion of the 

vegetated zone staying inundated during moderately high water years. Characteristic 

species include Eriocaulon aquaticum (pipewort) (sparse to abundant), Lobelia 

dortmanna (water lobelia), Isoetes tuckermanii (Tuckerman's quillwort) and other 

Isoetes, Scirpus pungens (three-square rush), Utricularia gibba (humped bladderwort), 

and submersed aquatic forms of Sagittaria graminea (grass-leaved arrowhead), Gratiola 

aurea (golden-pert), Juncus pelocarpus (mud rush), Eleocharis acicularis (least spikerush), 

and Sparganium americanum (lesser bur-reed). 

Dense to intermittent, permanently flooded rhizomatous stands of Scirpus pungens (threesquare 

rush) or Juncus militaris (bayonet rush) have been observed in New Hampshire along 

shallow sandy shores, but were not quantitatively sampled in this study. These may deserve 

recognition as distinct types upon further research and field sampling in the state, and occur in 

other New England states (Sorrie 1994). 

SAND PLAIN CLOSED-BASIN MARSH SETTINGS 

• Dense blueberry-winterberry-mountain holly tall shrub thicket (S4) 

Dense Vaccinium-Ilex-Nemopanthus tall shrub thicket 

This is a tall shrub community found at the margin of nearly all basin marshes, dominated by 

Vaccinium corymbosum (highbush blueberry) and Ilex verticillata (winterberry) and 

accompanied by lesser amounts of Lyonia ligustrina (male-berry), Chamaedaphne calyculata 

(leather-leaf), Nemopanthus mucronatus (mountain holly), Aronia arbutifolia (red chokeberry), 

Aronia melanocarpa (black chokeberry), and Rhododendron canadense (rhodora). 

These tall shrub thickets around basin marshes are considered a variant of a more broadly 

distributed shrub community described in the limnogenous/topogenous shrub thicket section 

(Vaccinium corymbosum-Ilex verticillata tall shrub thicket, dense Vaccinium-Ilex-Nemopanthus 

variant). 

• Robust graminoid/medium shrub/Sphagnum marsh (S3S4) 

This was a seasonally flooded complex of associations found in closed-basins and dominated 

by various robust perennial graminoids, medium shrubs, and Sphagnum mosses. It was typically 

positioned between dense Vaccinium-Ilex-Nemopanthus tall shrub thickets and various short 

graminoid and forb zones (e.g., Rhexia virginica-Eleocharis tenuis-Panicum spretum- 

Muhlenbergia uniflora sand plain marsh, Dulichium arundinaceum-Eleocharis smallii -Glyceria 


orealis-Puccinellia fernaldii mud flat marsh, or Eleocharis obtusa/olivacea-floating-leaved 

aquatic mud flat). Spiraea alba (meadow-sweet) was frequent and often a dominant but an 

abundance of Sphagnum moss (mostly Sphagnum cuspidatum) and

(lance-leaved violet), Juncus pelocarpus (mud rush), Hypericum boreale (northern St. John's-wort), 

Xyris difformis (robust yellow-eyed grass), Cyperus dentatus (bulblet umbrella-sedge), and 

Eriocaulon aquaticum (pipewort). This community was similar to pond shore Cladium mariscoides 

sandy turf pond shore and Cyperus dentatus open sandy pond shore, but differed by a greater 

abundance of short rhizomatous and clumped sedges, and fewer ruderals and tall graminoids than 

Cladium mariscoides sandy turf pond shore and Cyperus dentatus open sandy pond shore. All three 

are rare and declining communities in New Hampshire. Dulichium arundinaceum-Eleocharis 

smallii -Glyceria borealis-Puccinellia fernaldii mud flat marsh occupied approximately the same 

topographic position as this community (both begin ca. 0.75 m on average below the upland 

transition), but tended to have more organic matter accumulation, perhaps driven by less 

dramatically fluctuating water levels that lead to more organic matter production and accumulation. 

One basin that was classified to Cyperus dentatus open sandy pond shore was transitional to this 

type and contained the rare coastal plain species Scleria reticularis (stone nut-rush)* (disjunct from 

southeastern Massachusetts; Sperduto 1996), and other rare species including Euthamia tenuifolia 

(fine grass-leaved goldenrod)* and Lindernia anagallidea (false pimpernel)*. 

Ninety-five percent of water inputs at New Hampshire’s only site for this community came in 

the form of precipitation, with the remainder from ground water in-flow (Owen 1999). Drawdowns 

usually occur by late summer (earlier in dry years), stranding the aquatic Sphagnum 

cuspidatum as thin dry mats on mucky sand. From 1996-1999, water fluctuations averaged 1.76 

m/year, with a maximum range of 2.2 m recorded during the four-year period (Owen 1999). 

Soils were shallow sandy muck (10-20 cm) over sand. 

• Three-way sedge-Small’s spike-rush-manna-grass mud flat marsh (S2S3) 

Dulichium arundinaceum-Eleocharis smallii-Glyceria borealis-Puccinellia fernaldii mud flat marsh 

This was a densely vegetated, semi-permanently flooded “mud flat” community found in 

mucky basins dominated by short forbs and graminoids (

Frequent characteristic species included the aerenchymatous Dulichium arundinaceum 

(three-way sedge) (usually a dominant); floating-stemmed species Glyceria borealis (northern 

floating manna-grass) and Puccinellia pallida (pale manna-grass); short rhizomatous graminoids 

including Eleocharis smallii (Small's spike-rush), Eleocharis flavescens var. olivacea (olivebrown 

spike-rush), and Juncus pelocarpus (mud rush); and rhizomatous forbs including 

Hypericum boreale (northern St. John's-wort), Triadenum virginicum (marsh St. John's-wort), 

Viola lanceolata (lance-leaved violet), and Lysimachia terrestris (swamp candles). Tall 

graminoids were occasional and in moderately low abundance including Carex vesicaria 

(inflated sedge) and Carex utriculata (bottle-shaped sedge). Sphagnum was occasional and in 

low abundance. Mud flat annuals were frequent as a group, but inconsistent as to species and 

occasionally abundant including Eleocharis obtusa (blunt spike-rush), Lindernia dubia (common 

false pimpernel), Scirpus smithii (Smith's bulrush), Bidens connata (swamp beggar-ticks), Bidens 

frondosa (common beggar-ticks), and Erechtites hieracifolia (fireweed). 

Soils had 20-110 cm (average=57 cm) of O plus A horizon muck over sand, gravel, or 

slightly silty-gravelly sand. Measurements at individual sites were: 35-45 cm muck over coarse 

gravel (Hollis Depot) or sand (Turkey Hill); 60 cm slightly silty muck over slightly silty-gravelly 

gray sand to >1.2 m; 25 cm muck over sand (Rocky Hill Pond); 50-60 cm of silty muck over 

compact fine sand or silty fine sand to >1.2 m (Willand Pond); 50-60 cm of mucky peat over 

gravel to >1.2 m (Bragdon Ledge). 

• Blunt & olive-brown spike-rush-floating-leaved aquatic mud flat (S1) 

Eleocharis obtusa/olivacea-floating-leaved aquatic mud flat 

This was an intermittently exposed, moderately to densely vegetated community found on 

deep muck soils of closed basins, typically below Dulichium arundinaceum-Eleocharis smallii - 

Glyceria borealis-Puccinellia fernaldii mud flat marsh. During draw-down periods, short 

rhizomatous graminoids and forbs and mud flat annuals emerge along with aerenchymatous 

species and stranded floating-leaved and submerged aquatic species. Perennial, short 

rhizomatous species included Eleocharis flavescens var. olivacea (olive-brown spike-rush), 

Eleocharis smallii (Small's spike-rush), Eleocharis acicularis (least spike-rush), Juncus 

pelocarpus (mud rush), Scirpus torreyi (Torrey's threesquare), Hypericum boreale (northern St. 

John's-wort), Gratiola aurea (golden-pert), and Polygonum hydropiperoides (mild water 

pepper). The floating stemmed graminoid Glyceria borealis (northern floating manna-grass) was 

occasional. Characteristic mud flat annuals included frequent Eleocharis obtusa (blunt spikerush) 

and Scirpus smithii (Smith's bulrush), and occasional Panicum tuckermanii (Tuckerman's 

panic-grass), Bidens connata (swamp beggar-ticks)Panicum rigidulum (stiff panic-grass), 

Eleocharis ovata (ovoid spike-rush), Bidens discoidea (small bidens), and Erechtites hieracifolia 

(fireweed). Floating-leaved aquatics included Nuphar variegata (variegated yellow pond-lily), 

Potamogeton oakesianus (Oakes' pondweed), and Potamogeton diversifolius var. trichophyllus 

(common snailseed pondweed); submersed aquatics were also occasional, including 

Myriophyllum humile (low water-milfoil) and Utricularia radiata (inflated bladderwort). 


Aerenchymatous species included Sparganium americanum (lesser bur-reed). Eriocaulon 

aquaticum (pipewort) was occasional. This community occurred in wetter settings than 

Dulichium arundinaceum-Eleocharis smallii -Glyceria borealis-Puccinellia fernaldii mud flat 

marsh and differed from it by a lack of any tall graminoids and a greater abundance of floating 

and/or submersed aquatics. Soils consisted of 100 cm of muck (up to 73% organic matter) at 

Turkey Hill, 100 cm muck over sand at Rocky Hill, and 50 cm muck over sand and gravel at 

Hollis. 

• Sharp-flowered manna-grass shallow peat marsh (S1) 

Glyceria acutiflora shallow peat marsh 

This wetland community was characterized by semi-permanently flooded to intermittently 

exposed shallow peat swales dominated by the floating-stemmed Glyceria acutiflora (sharpflowered 

manna-grass)*. Sphagnum spp. (including S. cuspidatum) varied from being present in 

low abundance to being codominant with the Glyceria. Drawdown periods produce habitat for 

mud flat ruderals such as Scirpus smithii (Smith's bulrush), Polygonum pensylvanicum 

(Pennsylvania smartweed), Bidens cernua (nodding bur-marigold), Bidens frondosa (common 

beggar-ticks), Bidens connata (swamp beggar-ticks), Erechtites hieracifolia (fireweed), and 

Panicum dichotomiflorum (fall panic-grass), and for seedling establishment of Glyceria 

acutiflora. At the time of sampling the lower central zones were dominated by seedlings of 

Glyceria acutiflora surrounded by mature fruiting plants in the outer zone, rooting at the nodes. 

Other vegetation was sparse but included Glyceria canadensis (rattlesnake manna-grass), 

Callitriche heterophylla (diverse-leaved water starwort), Potamogeton oakesianus (Oakes' 

pondweed), Panicum tuckermanii (Tuckerman's panic-grass), and Nuphar variegata (variegated 

yellow pond-lily). This type is presently known from a single complex of basins in New 

Hampshire, where Glyceria acutiflora reaches the north end of its range. Soils contained 10-35 

cm of well decomposed peat over a shallow sandy muck layer over sand to >1.2 m (histic and 

mineral histic epipedons). 

• Northern basin marsh (S1) 

Only a few basin marshes have been located in the White Mountain region and one in 

Stewartstown. Coastal plain species are absent and more common marsh plants are 

characteristic. Some of these include Juncus canadensis (Canada rush), Glyceria borealis 

(northern floating manna-grass), Scirpus subterminalis (water bulrush), Osmunda regalis (royal 

fern), Spiraea latifolia (meadow-sweet), Iris versicolor (northern blue flag), Puccinellia pallida 

(pale manna-grass), Juncus pelocarpus (mud rush), and Bidens frondosa (common beggar-ticks). 

The basins in the White Mountains tend to have larger watersheds than more southern examples 

and have very broad fluctuations in water levels of up to two meters or more between spring and 

late summer. They are primarily found at the interface of mountain slopes and mixed outwash 

deposits of the Saco River valley. Good examples occur at Bragdon Ledge (Albany) and 

Sugarloaf Basins (Albany). 


COASTAL SAND DUNE SETTINGS 

• Coastal interdunal marsh/swale (S1) 

A freshwater wetland community found in sandy depressions between sand dunes (based on 

Dunlop and Crow (1985)). Dominants vary from swale to swale and include two types: a 

Vaccinium macrocarpon (large cranberry) type and a Juncus balticus (rush) type. Marginal 

associates include Aronia prunifolia (chokeberry), Ilex verticillata (winterberry), Toxicodendron 

radicans (poison ivy), and Triadenum virginicum (marsh St. John's-wort). Only a small dune 

system remains in Seabrook, NH. 


AQUATIC BED COMMUNITIES 

Aquatic bed communities have been poorly described at the association (community) level in 

New Hampshire. Differentiation of types will likely relate to water depth and periodicity, floodenergy 

and organic matter accumulation, and nutrient status of the adjacent water body. At this 

time only a few broadly defined types are noted, and these should not be considered inclusive of 

all examples (i.e., they are not an adequate system of “pigeon holes”). Aquatic bed communities 

have been more thoroughly sampled along sandy pond shores and closed-basin sand plain 

marshes. These are described in a separate section of the classification. 

Some rare floating-leaved or submersed aquatic species found in quiet, deep water or 

submersed along shallow shores of rivers or ponds include several Potamogeton species 

(pondweeds, see tracking list), Hippuris vulgaris (common mare’s tale)*, Megalodonta beckii 

(water marigold)*, Sagittaria cuneata (wapato)*, Lemna valdiviana (linear duckweed)*, Lemna 

trisulca (star duckweed)*, Isoetes engelmannii (Engelmann’s quillwort)*, Isoetes macrospora 

(large-spored quillwort)*, and Ranunculus subrigidus (stiff water crowfoot)*. 

• River rapids (S3) 

River rapids may alternatively be considered a type of riverine community, but are included 

here since many examples have rooted vascular plants in the shallow water conditions. River 

rapids are poorly sampled in the state, and the current description is based on examples from the 

Lamprey River (based on NH Heritage field surveys and Sperduto and Crow (1994)). 

Podostemum ceratophyllum (riverweed) is characteristic of some river rapids, including 

some along the Lamprey River system. This is a clonal plant that is restricted to river rapids, 

where it forms a low mat on submerged rocks. Other plants growing directly in the fast-flowing 

waters of the Lamprey include Ranunculus trichophyllus (white water crowfoot) and 

Potamogeton nodosus (knotty pondweed)*. 

The most notable areas along the Lamprey are at Packers Falls, Wadley (Wadleigh) Falls, the 

rapids at Lee Hook Road, several small sets of rapids between Wadley Falls and Lee Hook Road, 

and just downstream from the Main Street bridge in Epping. While riverweed is not presently 

tracked as a rare plant by NH Heritage, but is being considered as a candidate for tracking and 

listing. The habitat is quite specific, and due to its clonal growth, each river system might be 

considered a population. A study by Philbrick and Crow (1992) on genetic variation (including 

five sites on the Lamprey River) found no genetic variation within a river system and very little 

variation between river systems. In contrast, populations south of the glacial boundary were 

found to have a number of genotypes within a single set of rapids. During the spring and early 

summer the water levels are typically high, and species adapted to the swift-flowing water 

become well established. This is the peak time of development for Podostemum ceratophyllum 

(riverweed). Later in the season, as water levels drop, many rocks in the river and near the 

riverbank become exposed. At this time Podostemum ceratophyllum, attached to these rocks in 

the rapids, comes into flower, then fruits and dies back. Many other species begin to emerge and 


flower as well. When the riverbank plants are included (immediately adjacent to the rapids), 

species richness was relatively high for the typically small areas (40-60 vascular species for a 

section of rapids, generally 30-60 m (100-200 ft.) of shoreline). 

• Yellow pond lily-pickerelweed-pondweed aquatic beds (S4S5) 

This is a broadly defined and poorly sampled community that includes quiet, acidic, shallowwater 

communities of ponds, lakes, or slow-moving streams dominated by floating leaved, 

submersed, and emergent herbaceous species, with water depths typically of at least 0.6-0.9 m 

(2-3 ft.) in mid-late summer or shallower but permanent water. Deep emergent marshes are 

treated separately and include vegetation of littoral zones consisting primarily emergent rather 

than floating or submersed species and generally less than 0.6-0.9 m (2-3 ft.) of water. Many 

associations could be identified with additional sampling, but are not presently described well 

enough to enumerate. Common aquatic species in these communities include Nuphar variegata 

(yellow pond lily), Pontederia cordata (pickerelweed), Vallisneria americana (tape-grass), 

Potamogeton spp. (pondweeds), Brasenia schreberi (water-shield), Eleocharis acicularis (least 

spikerush), Myriophyllum humile (water milfoil), Nymphoides cordata (floating heart), 

Utricularia spp. (bladderworts), Lemna minor (lesser duckweed), and aquatic Polygonum species 

(smartweeds). 

Examples studied along coastal plain pond shores had the following species in addition to 

those specified above: Scirpus subterminalis (subterminal sedge), Potamogeton confervoides 

(Tuckerman's pondweed), Polygonum hydropiperoides (water smartweed), Utricularia vulgaris 

(common bladderwort), Utricularia gibba (humped bladderwort), Utricularia radiata (inflated 

bladderwort), and Utricularia intermedia (milfoil bladderwort). Other species observed during a 

study of the Lamprey River corridor include Ceratophyllum demersum (coontail), Myriophyllum 

verticillatum (a native milfoil), Megalodonta beckii (water marigold)*, Potamogeton epihydrus 

(surface pondweed), Potamogeton natans (floating pondweed), Potamogeton robbinsii (Robbin's 

pondweed), Utricularia purpurea (purple bladderwort), Spirodela polyrhiza (water-flaxseed), 

and Wolffia columbiana (water-meal). 


OPEN PEATLAND COMMUNITIES 

The open peatland natural community classification groups communities into five categories 

based on vegetation structure: (1) mud-bottoms, open moss lawns, and flarks; (2) dwarf- and 

medium-shrub bogs and poor fens; (3) sedge and shrub/graminoid fens; (4) tall shrub 

thicket/sparse woodlands; and (5) marshy peatland margin communities. There are 26 natural 

community types within these groups, which are arranged in the classification by trophic level 

(ranging from oligotrophic to minerotrophic). Many community types are widespread, some are 

geographically restricted, and a few are state and regionally rare. Rare types include calcareous 

patterned fen, acidic patterned fen, calcareous sedge/moss fen, all sloping and level 

alpine/subalpine peatlands, montane peatlands dominated by Calamagrostis pickeringii 

(Pickering's reed bent-grass), and some intermediate fens and seepage marshes. 

The terms “bog” and “fen” have been used in many different ways. From a long-term 

peatland-development perspective, the term “bog” is usually applied only to ombrogenous 

peatlands that are rain-fed. In this sense, New Hampshire has no known true bogs, but does 

contain a wide variety of “fens,” or peatlands whose development is controlled in part by 

topogenous, limnogenous, or soligenous sources of water. Floristically, however, New 

Hampshire does contain peatland vegetation that is largely isolated from the influence of upland 

runoff, stream or lake water, or seepage, and thus is similar to vegetation that occurs in 

ombrogenous settings. We apply the term “bog” to plant communities that have pHs below 4.0 

and only have species restricted to oligotrophic conditions. Other peatlands are considered fens. 

The 4.0 cutoff was shown by Wells (1996) to be a significant and convenient cutoff in Atlantic 

Canada peatlands. In these peatlands, pHs of 4.0 corresponded well to specific levels of calcium, 

iron, nitrogen, and magnesium that marked the transition from ombrotrophic conditions of bogs 

to the more minerotrophic conditions of fens. Our results in Sperduto et al. (2000) are consistent 

with this cut-off as evidenced by the absence of species indicative of minerotrophic conditions at 

pHs below 4.0 in most plots. Using these terms in reference to whole-peatland sites can be 

misleading because many peatland basins contain both fen and bog communities. 

It is also important to recognize that the vegetation of bogs and fens change at different rates 

depending on conditions. They may be quite stable over long periods, can change slowly over 

long time frames as peat accumulates, or can undergo rapid change and succession over much 

shorter time frames in response to natural or human disturbances. For example, peatlands in lake 

basins or those associated with streams may be periodically flooded by beavers. Flooding can 

result in significant vegetation changes in peatlands, particularly if the peat mat is grounded 

instead of floating (Mitchell and Niering 1993). Emergent marsh and aquatic vegetation can 

become established where ericaceous shrubs once grew. However, over the long term water 

levels could change or peat build-up could resume as the basin continues to accumulate organic 

matter. Even kettle hole bogs, which are commonly thought to have relatively stable water 

levels, have been shown to exhibit broad fluctuations and corresponding changes in vegetation 

(Miller 1996). 


MUD-BOTTOMS, OPEN MOSS LAWNS, AND FLARKS 

The following natural communities are saturated open Sphagnum moss, liverwort, or other 

non-vascular plant dominated lawns or carpets with a sparse, dwarf heath shrub layer. Heath 

shrubs average less than 15% cover and are less than 0.5 m in height in all communities, 

although there is some variation among individual plots. Peat is usually poorly decomposed near 

the surface and hummocks are weakly developed (average height is less than 0.15 m in all 

communities). Rhynchospora alba (white beak-rush) is occasional to frequent in all 

communities, and peat mosses are usually dominant. 

Mud-bottom and open moss lawn communities can be divided into oligotrophic (very acidic), 

weakly minerotrophic, and minerotrophic communities. The more oligotrophic communities are 

indicated by Vaccinium oxycoccos (small cranberry), Sphagnum rubellum, and low pHs (

In this community, peat is typically poorly decomposed near the surface and has a relatively 

flat surface profile (hummocks are generally

lasiocarpa/Myrica gale-Vaccinium macrocarpon sedge fen) by the abundance of aquatic Sphagna; 

the higher frequency of “bog” plants such as Eriophorum virginicum (tawny cotton-grass) and 

Sarracenia purpurea (pitcher-plant); the lower frequency of certain Carex species; and the absence 

of Sphagnum lescurii. The Sphagnum pulchrum – Carex moss lawn natural community sometimes 

has more acidic indicators than do the other natural communities in this group. Some examples 

may be intermediate among the three oligotrophic-weakly minerotrophic communities. 

• Sphagnum pulchrum/sedge moss lawn (S2S3) 

Sphagnum pulchrum/Carex moss lawn 

This natural community corresponds to open moss lawns or pools dominated by Sphagnum 

pulchrum. The community occurs as small pools with loose Sphagnum carpets, or occasionally 

as extensive lawns associated with large lake border peatlands (e.g., peatlands around Lake 

Umbagog). Vascular plants are sparse but may include Vaccinium oxycoccos (small cranberry), 

Carex limosa (quagmire sedge), Carex oligosperma (few seeded sedge), Carex utriculata 

(bottle-shaped sedge), Carex canescens (silvery sedge), Scheuchzeria palustris (pod-grass), 

Smilacina trifolia (three-leaved false Solomon's seal), Sarracenia purpurea (pitcher-plant), and 

Andromeda glaucophylla (bog rosemary). These moss lawns or pools range from oligotrophic to 

weakly minerotrophic in nutrient status (average pH is 4.0); more minerotrophic examples along 

lake borders contain species such as Myrica gale (sweet gale), Sphagnum affine, and S. 

papillosum. Sphagnum torreyanum and S. angustifolium are present in some examples. Trees 

and tall shrubs are always absent. 

This community is broadly distributed in the state. Heath shrubs are typically dwarfed 

(average height 0.30 m), hummocks are poorly developed, and peat is poorly decomposed. 

• Sphagnum cuspidatum/large cranberry moss lawn (S3) 

Sphagnum cuspidatum/Vaccinium macrocarpon moss lawn 

This community forms small to extensive floating peat mats in lake margin peatlands and in 

wet lagg areas along upland borders. Sphagnum cuspidatum is dominant and S. torreyanum is 

generally absent. Chamaedaphne calyculata (leather-leaf) is frequent and sometimes abundant. 

Vaccinium macrocarpon (large cranberry), Carex canescens (silvery sedge), and Myrica gale 

(sweet gale) are common in low to moderate abundance, and Rhynchospora alba (white beakrush), 

Sarracenia purpurea (pitcher-plant), and Eriophorum virginicum (tawny cotton-grass) are 

occasional. Sphagnum angustifolium, S. fimbriatum, and S. fallax are infrequent. Robust Carex 

species (Carex lasiocarpa var. americana (hairy-fruited sedge), C. utriculata (bottle-shaped 

sedge), and C. oligosperma (few seeded sedge)) are infrequent. 

This natural community is widespread in New Hampshire. The average pH is 4.2, and 

hummocks are moderately small (average hummock height 0.11 m; average maximum hummock 

height 0.20 m). Peat is moderately well decomposed in the upper 0.5 m. Dwarf shrub height 

averages 0.29 m. 


A rare variant is dominated by the coastal plain sedge Carex bullata (inflated sedge)* and 

Sphagnum cuspidatum. Although known from only one peatland site in the state, this variant is 

probably more widespread farther south on the coastal plain and likely deserves community-level 

status. 

• Sphagnum torreyanum/large cranberry/white beak-rush moss lawn (S3) 

Sphagnum torreyanum/Vaccinium macrocarpon/Rhynchospora alba moss lawn 

Like the Sphagnum cuspidatum – Vaccinium macrocarpon moss lawns described above, this 

community also forms small to extensive floating peat mats in lake margin peatlands and in wet 

lagg areas along upland borders. Sphagnum torreyanum is abundant to dominant, S. papillosum 

is occasional, and S. affine, S. pulchrum, and S. cuspidatum are infrequent. Dulichium 

arundinaceum (three-way sedge), Vaccinium macrocarpon (large cranberry), Carex canescens 

(silvery sedge), and Myrica gale (sweet gale) are common in low to moderate abundance and are 

indicative of weakly minerotrophic conditions. Rhynchospora alba (white beak-rush) is 

frequent, and Juncus pelocarpus (mud rush), Drosera intermedia (spatulate-leaved sundew), 

Sarracenia purpurea (pitcher-plant), and Eriophorum virginicum (tawny cotton-grass) are 

occasional. Scheuchzeria palustris (pod-grass), Carex lasiocarpa var. americana (hairy-fruited 

sedge), C. utriculata (bottle-shaped sedge), C. oligosperma (few seeded sedge), and C. limosa 

(quagmire sedge) are infrequent. 

This community occurs mostly in central and southern New Hampshire but is occasional in 

the northern part of the state as well. Average pH is 4.3. Hummocks are moderately small 

(average 0.14 m (0.08)) and range to an average maximum height of 0.29 m. Peat is moderately 

well decomposed within the upper 0.5 m. Dwarf shrub height averages 0.42 m. 

MINEROTROPHIC TYPES (CIRCUMNEUTRAL – CALCAREOUS) 

• Circumneutral-calcareous flark (S1) 

In New Hampshire, patterned fens are known to occur at only two sites and are otherwise 

restricted in New England to the more boreal climate of northern Maine. Of the two occurrences 

in New Hampshire, one site supports an acidic fen and the other has circumneutral-calcareous 

conditions. Slow groundwater movement through the gently sloping wetland causes the 

patterned or “ribbed” fen topography. 

Circumneutral-calcareous flarks and flark borders at the single, northern New Hampshire site 

are characterized by saturated to flooded hollows lying approximately parallel to low peat ridges 

(strings or ribs) in the patterned fen. Vegetation is characterized by an abundant brown algal 

mat, low vascular plant cover (ca. 12%), and sparse cover of Sphagnum contortum (ca. 5%). 

Herbaceous plants include Carex exilis (meagre sedge)*, Menyanthes trifoliata (buckbean), 

Scirpus hudsonianus (northern cotton club rush), Utricularia minor (small bladderwort), 

Sarracenia purpurea (pitcher-plant), Rhynchospora alba (white beak-rush), Drosera intermedia 

(spatulate-leaved sundew), Eriophorum viridicarinatum (green keeled cotton-grass), Andromeda 


glaucophylla (bog rosemary), Solidago c.f. purshii (Pursh's goldenrod)*, Carex livida (glaucous 

sedge)*, Juncus stygius (styx rush)*, Carex tenuiflora (thin-flowered sedge)*, and Muhlenbergia 

glomerata (clustered marsh muhly). 

The flarks range from a few meters to more than 25 m wide with pHs ranging from 6.3 – 8.4 

(-9.0). The sparse shrub cover (

(bilberry)*, and Rubus chamaemorus (baked apple berry)*. Sphagnum fuscum and S. 

capillifolium are the most common peat moss species. Others may include Sphagnum rubellum, 

S. russowii, and S. lescurii. This community is more permanently saturated than the subalpine 

wooded heath snowbank, slope bog, and bog margin communities described below, as indicated 

by the presence of Vaccinium oxycoccos (small cranberry), Eriophorum vaginatum (cotton 

grass), and other species indicative of saturated conditions, and usually by the absence of 

Cetraria islandica and other lichens. Sphagnum is a constant. Ledum groenlandicum (Labradortea) 

is nearly constant and other heath shrubs are frequent, including Chamaedaphne calyculata 

(leather-leaf), Kalmia angustifolia (sheep laurel), and Kalmia polifolia (bog laurel). Two 

variants are recognized: 

1. Rubus chamaemorus-Scirpus cespitosus-Vaccinium uliginosum variant: This variant 

differs from the next by a higher frequency of Vaccinium uliginosum var. alpinum 

(bilberry)*, Rubus chamaemorus (baked apple berry)*, and Scirpus cespitosus (tussock 

bulrush). Vaccinium vitis-idaea (mountain cranberry) is occasional. Rhododendron 

canadense (rhodora) is absent. This variant can occur at higher elevations (up to ca. 4900 

ft.) than the one described below. 

2. Rhododendron canadense/shrub heath variant: This variant tends to lack Scirpus 

cespitosus (tussock bulrush) and Rubus chamaemorus (baked apple berry)*, has less 

Vaccinium uliginosum var. alpinum (bilberry)*, and often has a denser cover of dwarf 

shrubs. Empetrum nigrum (black crowberry)* is occasional, while Rhododendron 

canadense (rhodora) is frequent. Picea mariana (black spruce) is more frequent and 

abundant compared to the preceding variant. The Rhododendron canadense/shrub heath 

variant occurs at a maximum elevation of ca. 3700 ft. and is transitional to the subalpine 

wooded heath snowbank, slope bog, and bog margin community. 

• Subalpine wooded heath snowbank, slope bog, and bog margin (S1S2) 

Picea mariana – Abies balsamea/Sphagnum/Cetraria islandica heath snowbank/bog border 

This community is found in subalpine settings where deeper snows accumulate (e.g., on lee 

slopes of peaks or near krummholz margins), on drier borders of bogs, and on other moist slopes 

where Sphagnum maintains growth and peat accumulates. This community is intermediate 

between wet bogs and heath/krummholz communities. It differs from wetter alpine bogs by a 

generally higher cover of Picea mariana and Abies balsamea krummholz (stunted trees

• Subalpine sliding fen (S1) 

Calamagrostis pickeringii-Scirpus cespitosus/Sphagnum compactum sliding fen 

This shallow peat bog community occurs on 5-30 o slopes along the brow of alpine/subalpine 

cliffs at one site in the White Mountains. It is floristically similar to other alpine/subalpine bogs 

but differs by the abundance of Calamagrostis pickeringii (Pickering's reed bent-grass)*, 

Sphagnum compactum, and Geum peckii (mountain avens)*. Scirpus cespitosus (tussock 

bulrush), Sphagnum russowii, S. capillifolium, and S. girgensohnii are abundant, along with 

various heath shrubs. Elsewhere in the region, sliding fens can presumably become supersaturated 

from a major rain event and slide off the cliff (hence the name) before peat build-up 

resumes (pers. comm., David Hunt 1999). This is a very rare community in the state with a 

single documented example on top of Cannon Cliff. A few other high-elevation cliffs in the 

White Mountains may also contain examples of this community. 

OLIGOTROPHIC – WEAKLY MINEROTROPHIC MID-LOW ELEVATION BOGS AND POOR SHRUB FENS 

(VERY ACIDIC – ACIDIC) 

• Leather-leaf-sheep laurel/Sphagnum capillifolium dwarf heath shrub bog (S1 and S3) 

Chamaedaphne calyculata-Kalmia angustifolia/Sphagnum capillifolium dwarf heath shrub bog 

This community is characterized by oligotrophic to weakly minerotrophic bogs and poor fens 

dominated by a low diversity but dense cover of dwarf- to medium-height heath shrubs, and an 

absence or very low abundance of tall shrubs and trees. Chamaedaphne calyculata (leather-leaf) 

is the dominant shrub, with lesser quantities of Kalmia angustifolia (sheep laurel) and sometimes 

Rhododendron canadense (rhodora). Sphagnum capillifolium is diagnostic and typically 

occupies hummocks. Other abundant Sphagna include Sphagnum magellanicum and S. 

rubellum, while S. angustifolium is occasional. Polytrichum strictum is common on hummocks, 

and Carex trisperma var. billingsii (Billing's sedge) is occasional. This community has a higher 

constancy of S. capillifolium and apparent lower frequency of Picea mariana (black spruce) than 

the Chamaedaphne calyculata-Kalmia angustifolia/Picea mariana dwarf heath shrub bog/very 

poor fen community described below. Scattered individuals of black spruce may occur, 

however, across the larger matrix of vegetation at some sites. 

Hummock and hollow topography is well developed with average and average-maximum 

hummock heights of 0.24 m and 0.40 m, respectively. Average pH is 3.8. Shrubs average 0.52 

m in height and form a relatively dense cover (35-50%) compared to other peatland 

communities. This community is documented from central and southern New Hampshire, but it 

is probably widespread in the state. 

Three variants can be recognized: 

1. Dwarf-medium heath shrub bog variant (S3): Sphagnum flexuosum and S. papillosum 

are absent (average pH is 3.8), but Kalmia angustifolia (sheep laurel), S. magellanicum, 

and S. capillifolium are more prominent than in the other variants. Shrub height averages 

0.60 m, but occasionally ranges to nearly 1 m in a few samples. 


2. Dwarf heath shrub bog variant (S1): Floristically, examples in this variant do not 

differ much from the oligotrophic dwarf medium shrub heath community above, but they 

are characterized by a shorter dwarf heath layer (shrub heights range from 0.30-0.35 m) 

and very oligotrophic to possibly ombrogenous conditions. This variant has very low 

vascular species richness compared to most other peatland communities and occupies 

hydrologically isolated portions of oligotrophic basin peatlands. Average pH is 3.5 

(range 3.3-3.7). These are the lowest pHs recorded among lowland peatlands in the state 

(below 1000 ft.), and they are comparable to or more acidic than those of many alpine 

bogs. 

3. Weakly minerotrophic heath shrub poor fen variant (S3): Sphagnum flexuosum and 

S. papillosum are indicative of weakly minerotrophic conditions in this variant compared 

to the others, although pHs are quite low (average pH is 3.9). Sphagnum magellanicum, 

S. capillifolium, and Kalmia angustifolia (sheep laurel) are absent or sparse. The 

presence of minerotrophic Sphagna aligns this variant with the Andromeda glaucophylla- 

Myrica gale-Carex utriculata/Sphagnum fallax fen community, and this variant could 

therefore be grouped with it. Shrub height averages ca. 0.60 m. 

• Leather-leaf-sheep laurel/black spruce dwarf heath shrub bog/very poor fen (S3) 

Chamaedaphne calyculata-Kalmia angustifolia/Picea mariana dwarf heath shrub bog/very poor fen 

This community corresponds to oligotrophic dwarf heath bogs or very poor fens with 

essentially no tall shrubs and a sparse, stunted tree canopy of Picea mariana (black spruce) 

and/or Larix laricina (eastern larch) (generally 1-10% cover and less than 1-6 m in height). It is 

structurally similar to “muskegs” in the boreal forest region. Some combination of Sphagnum 

angustifolium, S. rubellum, and/or S. magellanicum dominates the moss layer. Sphagnum 

capillifolium is occasional but not as frequent as in Chamaedaphne calyculata-Kalmia 

angustifolia/Sphagnum capillifolium dwarf heath shrub bogs. Eriophorum vaginatum var. 

spissum (hare's-tail), E. virginicum (tawny cotton-grass), Smilacina trifolia (three-leaved false 

Solomon's seal), and Carex trisperma var. billingsii (Billing's sedge) are frequent. 

Chamaedaphne calyculata (leather-leaf), Kalmia angustifolia (sheep laurel), Vaccinium 

oxycoccos (small cranberry), and Kalmia polifolia (bog laurel) are characteristic of the dwarf 

heath layer. 

Shrub height averages ca. 0.48 m, pH averages 3.8, and peat is poorly decomposed in the 

upper 0.5 m. Hummocks are moderately to very well developed. Canopy trees (above the tall 

shrub layer) average ca. 6 m in height. 

Two reasonably distinct variants are described: 

1. Sphagnum rubellum-S. angustifolium dwarf heath variant: This variant is most 

common in central and southern New Hampshire and is distinguished from the next 

variant by the lack of Ledum groenlandicum (Labrador-tea) and Sphagnum fuscum; a less 

developed hummock-hollow topography; a lower abundance of trees; and a generally 


stronger dominance of Sphagnum rubellum and S. angustifolium. Average pH is 3.7, 

heath shrubs are less than 0.5 m in height, and peat is poorly decomposed in the upper 

0.75 m. Hummocks average about 0.16 m, with a maximum height of less than 0.30 m. 

2. Ledum groenlandicum-Sphagnum fuscum dwarf heath variant: This variant is most 

common in northern New Hampshire and is distinguished by the presence of Ledum 

groenlandicum (Labrador-tea) and Sphagnum fuscum; a better developed hummockhollow 

topography; and a higher abundance and structural complexity of the tree layer. 

Carex pauciflora (few-flowered sedge) is occasional. Hummock height averages 0.25 m, 

with maximum heights averaging 0.4 m. The average pH is 3.95. 

INTERMEDIATE – MINEROTROPHIC (CIRCUMNEUTRAL) TYPE 

• Northern white cedar circumneutral string (S1) 

Thuja occidentalis circumneutral string 

In New Hampshire, patterned fens are known to occur at only two sites and are otherwise 

restricted in New England to the more boreal climate of northern Maine. Of the two occurrences 

in New Hampshire, one site supports an acidic or “poor” fen and the other has circumneutralcalcareous 

conditions. Slow groundwater movement through the gently sloping wetland causes 

the patterned or “ribbed” fen micro-topography. 

Circumneutral strings or “ribs” at the single, northern New Hampshire site are characterized 

by saturated, low peat ridges lying approximately parallel to saturated or flooded circumneutralcalcareous 

flarks. The strings are dominated by stunted (and heavily browsed) Thuja 

occidentalis (northern white cedar), averaging 1 m tall (ranging from

SEDGE AND SHRUB/GRAMINOID FENS 

WEAKLY MINEROTROPHIC TYPES (ACIDIC) 

• Bog rosemary-sweet gale/bottle-shaped sedge/Sphagnum fallax fen (S3) 

Andromeda glaucophylla-Myrica gale/Carex utriculata/Sphagnum fallax fen 

These are weakly minerotrophic fens dominated by a mixture of dwarf shrubs, Carex species, 

and several Sphagna; trees and tall shrubs are sparse or absent. They differ from other fens that 

contain Myrica gale (sweet gale) and Carex utriculata (bottle-shaped sedge) in the abundance of 

Sphagnum fallax, S. angustifolium, and S. magellanicum, and some combination of Andromeda 

glaucophylla (bog rosemary), Kalmia polifolia (bog laurel), Vaccinium oxycoccos (small 

cranberry), and Smilacina trifolia (three-leaved false Solomon's seal). Chamaedaphne 

calyculata (leather-leaf) is usually a dominant, and Carex utriculata and/or Carex oligosperma 

(few seeded sedge) are frequently present. Carex paupercula (bog sedge), Carex lacustris (lake 

sedge), Symplocarpus foetidus (skunk cabbage), and Betula pumila (swamp birch)* are 

infrequent in the community overall but abundant in one example. Swamp birch is known from 

only one site in the state, in relatively acidic conditions. 

Shrub stature is dwarfed with an average height of 0.49 m. Average pH is 4.12. Hummocks 

are weakly developed (average height 0.16 m and usually

• Water willow/Sphagnum recurvum-S. flexuosum border thicket (S3) 

Decodon verticillatus/Sphagnum recurvum-S. flexuosum border thicket 

This community occurs in wet minerotrophic settings along pond borders, laggs, and other 

upland border situations. It is dominated by minerotrophic Sphagnum species including S. 

recurvum, S. flexuosum, S. fimbriatum, and occasionally S. papillosum. Decodon verticillatus 

(water willow) is usually but not always present, and it can occur in other communities. Other 

frequent species include Carex canescens (silvery sedge), Chamaedaphne calyculata (leatherleaf), 

Myrica gale (sweet gale), Lysimachia terrestris (swamp candles), and Triadenum 

virginicum (marsh St. John’s-wort). Vaccinium corymbosum (highbush blueberry) is infrequent 

and in low abundance. This community occurs in southern and central New Hampshire. 

Sphagnum recurvum and Decodon verticillatus have southern or coastal affinities. 

Average pH is 4.4, and hummocks are usually moderately well developed (average height 

0.25 m). Peat is relatively well decomposed near the surface. Average medium shrub height is 

0.95 m. This community occurs in southern and central New Hampshire. 

• Montane Pickering’s reed bent-grass/shrub level/sloping fen (S1) 

Montane Calamagrostis pickeringii/shrub level/sloping fen 

This community is restricted to the upper East Branch of the Pemigewasset River watershed 

near Shoal and Ethan Pond in the White Mountains above elevations of 2400 ft. It forms in level 

to sloping positions along slow drainages or seepy slopes lacking drainage channels. Climate, 

hydrologic conditions, and soil features are probably the primary factors contributing to the 

development of this unique wetland community. Structurally, this community is graminoidshrub 

dominated. This type co-occurs with weakly minerotrophic montane tall shrub 

thicket/sparse woodland communities with a high cover of medium to tall shrubs, scattered 

sapling-sized trees, and small graminoid/moss lawn openings. 

The vegetation is typically dominated by Calamagrostis pickeringii (Pickering's reed bentgrass)*, 

Carex oligosperma (few seeded sedge), and Carex echinata (prickly sedge). Sphagnum 

mosses are abundant. Although complete bryophyte surveys have not been conducted, 

documented species include Sphagnum subtile, S. angustifolium, and Sphagnum girgensohnii. 

Other occasional species include Vaccinium oxycoccos (small cranberry), Eriophorum 

virginicum (tawny cotton-grass), Sarracenia purpurea (pitcher-plant), Drosera rotundifolia 

(round-leaved sundew), Aster radula (rough-leaved aster), Carex trisperma var. trisperma 

(three-seeded sedge), Carex pauciflora (few-flowered sedge), Carex wiegandii (Wiegand's 

sedge)*, Coptis trifolia var. groenlandica (goldthread), Dalibarda repens (false violet), Juncus 

brevicaudatus (short-tailed rush), Platanthera clavellata (small green woodland orchid), and 

Solidago purshii (Pursh's goldenrod)*. Woody plants are sparse to frequent and may form a 

mosaic with moderate to large graminoid dominated areas. Shrubs and trees may include 

Rhododendron canadense (rhodora), Nemopanthus mucronatus (mountain holly), Viburnum 

nudum var. cassinoides (witherod), Larix laricina (eastern larch), Picea mariana (black spruce), 


Picea rubens (red spruce), Ledum groenlandicum (Labrador-tea), Vaccinium myrtilloides 

(velvet-leaf blueberry), and less frequently Alnus incana var. americana (speckled alder), Kalmia 

angustifolia (sheep laurel), and Amelanchier bartramiana (Bartram's serviceberry). 

Soils are characterized by shallow organics over hydric, cryic, silty gravels. Organic soil 

depths are generally deeper than those underlying the related montane alder-heath shrub thicket. 

At two sites, pH readings were 4.6 and 4.7. Hummock and hollow topography is moderately to 

poorly developed. 

INTERMEDIATE TYPES (SUBNEUTRAL) 

• Hairy-fruited sedge/sweet gale-large cranberry sedge fen (S3) 

Carex lasiocarpa/Myrica gale-Vaccinium macrocarpon sedge fen 

This is a widespread, intermediate (minerotrophic) fen community often associated with lake 

and pond margins. It is also occasional along upland borders of some kettle holes or along 

floating mats of lake-fill peatlands. Carex lasiocarpa var. americana (hairy-fruited sedge) and 

Myrica gale (sweet gale) are usually present. Carex utriculata (bottle-shaped sedge) is frequent, 

and Carex oligosperma (few seeded sedge) is occasional. At least one of these three sedge 

species is always present. Forbs indicative of intermediate nutrient status are usually present in 

low abundance, including Lysimachia terrestris (swamp candles), Triadenum virginicum (marsh 

St. John’s-wort), and Sagittaria latifolia (common arrowhead). Vaccinium macrocarpon (large 

cranberry) can be common but is not always present. Spiraea alba var. latifolia (eastern 

meadow-sweet), Calamagrostis canadensis (blue-joint), and Typha latifolia (common cat-tail) 

are occasional, particularly when Vaccinium macrocarpon is absent. Peltandra virginica (arrowarum) 

is occasional. Sphagnum may be absent but usually forms a sparse to moderate cover that 

may include Sphagnum lescurii (frequent) and S. torreyanum (occasional). Sphagnum 

cuspidatum, S. fimbriatum, and S. affine are uncommon. Chamaedaphne calyculata (leatherleaf) 

is occasional, but medium and tall shrubs and trees are sparse or absent. 

Average pH is 4.9. Hummocks are low to moderately sized (average height 0.19 m), and 

peat is moderately to well decomposed within the upper 0.5 m. Many examples along lakes 

consist of moderately shallow peat layers underlain by lake silts. 

• Speckled alder/lake sedge-skunk cabbage intermediate fen (S2S3) 

Alnus incana/Carex lacustris-Symplocarpus intermediate fen 

This is a minerotrophic fen community dominated by medium and tall shrubs and robust 

herbaceous species. The prominence of shrubs, deeper organic soil, and greater abundance of 

peat moss differentiates this community from graminoid-forb-sensitive fern seepage marshes; the 

abundance of herbs (25-90% cover) differentiates it from other fen communities; and the absence 

or low cover of trees in the overstory (

The tall shrub layer varies from 5-40% cover. Alnus incana var. americana (speckled alder) 

is usually the most abundant tall shrub. Others include Ilex verticillata (winterberry), Lyonia 

ligustrina (male-berry), Viburnum nudum var. cassinoides (witherod), and Vaccinium 

corymbosum (highbush blueberry). Medium shrubs are usually abundant (5-50% cover). 

Frequent species include Chamaedaphne calyculata (leather-leaf), Myrica gale (sweet gale), 

Rhododendron canadense (rhodora), Spiraea alba (meadow-sweet), Kalmia angustifolia (sheep 

laurel), Kalmia polifolia (bog laurel), and Andromeda glaucophylla (bog rosemary). The rare 

Betula pumila (swamp birch)* occurs in one example in the state. Trees may include Larix 

laricina (eastern larch), Picea mariana (black spruce), Acer rubrum (red maple), and Betula 

populifolia (gray birch). Robust herbs are abundant (25-90%). Frequent and abundant species 

include Carex lacustris (lake sedge), Symplocarpus foetidus (skunk cabbage), Osmunda regalis 

var. spectabilis (royal fern), and Osmunda cinnamomea (cinnamon fern). Less frequent or 

abundant herbs include Carex utriculata (bottle-shaped sedge), Carex oligosperma (few seeded 

sedge), Calla palustris (wild calla), Lysimachia terrestris (swamp candles), Triadenum 

virginicum (marsh St. John's-wort), Calamagrostis canadensis (blue-joint), and Smilacina 

trifolia (three-leaved false Solomon's seal). Peat mosses are abundant (20-80% cover) and 

include Sphagnum fallax, S. magellanicum, S. angustifolium, and S. flexuosum. 

This community presumably occurs where there is some seepage influence. Peat soils were 

one meter thick in three examples sampled over sand or loam materials. Poorly decomposed 

surface peat transitioned to well decomposed peat within 20-30 cm of the surface. Hummock 

and hollow topography is well developed. pHs range from 4.4 to 5.7. This community may 

occur throughout the state, but is presently documented from central and northern New 

Hampshire. 

INTERMEDIATE – MINEROTROPHIC (MESOTROPHIC) TYPES (CIRCUMNEUTRAL – CALCAREOUS) 

• Calcareous sedge/moss fen (S2) 

Carex flava-Carex interior/Campylium stellatum calcareous fen 

Calcareous sedge/moss fens occur in northern New Hampshire in a variety of "disturbed" or 

groundwater influenced hydrological settings where groundwater seepage has a year-round 

influence and contributes a relatively high proportion of the water budget. These settings include 

(1) headwater positions, (2) marginal areas of lakes and stream drainages through marshes or 

swamps, (3) beaver meadows, (4) gaps in calcareous seepage swamps (e.g., cedar swamps), (5) 

other small basins, kettles, or catchments with seepage influence, (6) steep terraces of major rivers 

or minor stream drainages where seepage emerges and more moderately sloping side slopes of hills, 

and (7) grazed pastures. All of these settings have some or a considerable level of seepage influence 

and a tendency to stay open to one degree or another, depending on other factors. In addition, 

disturbance intensity varies and may be either natural or artificial in character. 

Characteristic vegetation includes Carex interior (inland sedge), Carex flava (yellow sedge), 

Carex hystericina (porcupine sedge), Drosera rotundifolia (round-leaved sundew), Eleocharis 


tenuis (slender spike rush), Equisetum fluviatile (water horsetail), Eriophorum virginicum (tawny 

cottongrass), Geum rivale (water avens), Platanthera hyperborea (northern green orchis), 

Platanthera psycodes (purple-fringed orchid), Platanthera dilatata (white bog orchis), Scirpus 

hudsonianus (cotton bulrush), Scirpus rubrotinctus (=microcarpus) (red-tinged bulrush), Senecio 

robbinsii (Robbins ragwort), Thuja occidentalis (northern white cedar), and Typha latifolia 

(common cat-tail). Other species frequent in calcareous fens that may also occur in other habitats 

include Equisetum arvense (field-horsetail), Eupatorium maculatum (spotted Joe-pye-weed), 

Fragaria virginiana (wood strawberry), Glyceria striata (manna-grass), Hydrocotyle americanum 

(water pennywort), Juncus tenuis (=dudleyi) (path rush), Juncus nodosus (noded rush), Salix lucida 

(shinning willow), Salix discolor (large pussy willow), Salix bebbiana (long-beaked willow), and 

Thelypteris palustris (marsh fern). 

Rare plants occurring in calcareous fens include Spiranthes romanzoffiana (hooded ladies' 

tresses)*, Equisetum variegatum (variegated horsetail)*, Cypripedium reginae (showy lady's 

slipper)*, Lobelia kalmii (Kalm's lobelia)*, Petasites frigidus var. palmatus (sweet coltsfoot)*, 

Carex bebbii (Bebb's sedge)*, Carex castanea (chestnut sedge)*, Equisetum palustre (marsh 

horsetail)*, Equisetum pratense (meadow horsetail), Carex aurea (golden-fruited sedge)*, and 

Eleocharis pauciflora var. fernaldii (few-flowered spikerush)*. 

Bryophytes often found in calcareous fens include Aulocomnium palustre, Sphagnum 

warnstorfii, Tomenthypnum nitens, Mnium affine var. rugicum, Mnium cuspidatum, Bryum pseudotriquetrum, 

Campylium stellatum, Climaceum dendroides, Fissidens adianthoides, Helodium 

blandowii, Hypnum pratense, Lophoclea sp., Philinotus fontana, and Pellia epiphylla. 

Soils typically have shallow to moderate organic horizon depths (0.2-1.2+ m) of poorly to well 

decomposed peat (depending on depth). Muck or peaty muck layers are found at some sites, 

particularly in active pasture fens where there has presumably been more mixing of shallow peat 

with underlying mineral horizons due to bovine traffic. Underlying till, or less often outwash soils, 

invariably have a significant gravelly or stony silt or silty muck soil that impedes downward 

movement of water. 

Calcareous fens appear to have a strong correlation with bedrock and till source material 

containing a significant amount of calcium and other base-cations. Bedrock types in New 

Hampshire with these qualities include the Waits River, Fitch, and Ammonoosuc Volcanic 

Formations, and to a lesser extent syenites, diorites, Gile Mountain Formation, and others. 

Average pH is 7.2 and ranges from 6.7 to 8.2, with one aberrant pH of 6.2. Conductivity ranges 

from 90 to 380 uS, with two aberrant readings of 60 and 750. 

Floristic and environmental differences may vary significantly from site to site. Given this 

variability, and because there are only a few examples of each community known from New 

Hampshire, they are better viewed as variants rather than community types until their differences in 

composition, distribution, and landscape context are better understood. Any of the following 

variants may differ depending on the frequency, intensity, and timing of grazing by livestock. The 

more active the pasturing, the greater the prominence of non-native pasture grasses and forbs, and of 


native ruderals. Intense pasturing appears to mix peat and mineral horizons into shallow peatymucks. 

1. Sloping typic variant: This variant occurs on shallow peat (less than 0.5 m) and occurs in 

slightly sloping headwater positions of drainages and former pastures. 

2. Level/shallow sloping deep peat variant: This variant has deeper peats (0.5-1+ m) and is 

often found in more level positions or natural basins and drainage margins where basin 

morphology and hydrology has led to significant peat accumulations: often occurs as 

temporary to semi-permanent natural openings in Thuja occidentalis (northern white cedar) 

swamps. 

3. Steep slope Equisetum variant: This variant occurs on seepy, steep river terraces or 

headwater drainage positions with shallow peat and a strong prominence of Equisetum 

species (horsetails). 

4. Beaver meadow variant: This variant occurs in marsh drainages behind old beaver 

impoundments in calcareous regions. Few examples are known, but clearly these 

wetlands have a different long- and short-term disturbance regime. Orchids appear to be 

sparse, and certain graminoids may be more prominent in these situations than in the 

above variants (e.g., Carex utriculata (beaked sedge), Carex bebbii (Bebb's sedge)*, 

Calamagrostis canadensis (blue-joint), and the rare Eleocharis pauciflora var. fernaldii 

(few-flowered spikerush)*), but calciphiles are present, distinguishing this variant from 

typical beaver meadows. Presumably, a beaver meadow variant is also a temporary 

phase in a natural successional cycle either toward woody plants (with drainage or 

sedimentation of the meadow) or toward aquatic vegetation (when flooded). 

• Graminoid-forb-sensitive fern seepage marsh (S3) 

Seepage marshes occur in association with groundwater discharge zones near upland borders 

of various wetland types, in headwater positions, along stream drainages (including the interface 

of a drainage with a larger marsh), or in other areas where groundwater discharge is prominent. 

They tend to be larger than forest seeps and do not have a significant tree canopy influence, 

except along the borders. Seepage marshes are intermediate between fens and marshes both 

floristically and environmentally. All contain a mixture of graminoids, forbs, and ferns including 

indicators of seepage and minerotrophic conditions. All known examples have shallow peat or 

muck organic layers over silt or silty muck. Mosses may be abundant but Sphagnum is generally 

absent. At this time, specific communities or variants are not described, although floristic 

variation and distributional patterns suggest that several communities could be described with the 

collection of additional data. Examples dominated by Carex lacustris (lake sedge) are the most 

frequently observed and will likely be described as a distinct community in the future. 

Potential dominant species indicative of seepage or minerotrophic conditions include Onoclea 

sensibilis (sensitive fern) (high frequency among known examples), Carex lacustris (lake sedge), 

Eupatorium maculatum (spotted Joe-pye-weed), Osmunda regalis (royal fern), Thelypteris 


palustris (marsh fern), Symplocarpus foetidus (skunk cabbage), Saxifraga pensylvanica (swamp 

saxifrage), and Carex scabrata (scabrous sedge). Other minerotrophic indicators are usually 

present in lower abundance and may include Senecio robbinsii (Robbins ragwort), Hydrocotyle 

americana (common water pennywort), Chrysosplenium americanum (golden saxifrage), Carex 

stipata (awl sedge), Carex leptalea (delicate sedge), Carex prasina (drooping sedge), Impatiens 

capensis (spotted touch-me-not), Mentha arvensis (field mint), Toxicodendron vernix (poison 

sumac), Chelone glabra (white turtlehead), Lysimachia terrestris (swamp candles), and Equisetum 

fluviatile (water horsetail). Other occasionally abundant species indicative of at least weakly 

minerotrophic conditions may include Calamagrostis canadensis (blue-joint), Equisetum arvense 

(field horsetail), Aster puniceus (purple stemmed aster), Potentilla palustris (marsh cinquefoil), 

Spiraea alba (meadow-sweet), and Carex lasiocarpa var. americana (hairy-fruited sedge). 

Mosses include Mnium spp. and Philinotis fontana, among many others. Other common marsh 

plants may be present as well, including Carex lurida (sallow sedge). Soils tend to be shallow 

fibric peats or mucks over silts or silty sands. In four examples, pHs range from 5.5 to 6.3, 

indicating subneutral-circumneutral conditions. 

TALL – MEDIUM SHRUB THICKET/SPARSE WOODLANDS 

Tall – medium shrub thicket peatlands usually occur as part of a mosaic with other peatland 

communities, but they can be the primary community in some peatland basins. Compared to 

peatlands dominated by shorter vascular plants, the presence of tall shrubs is usually associated 

with some combination of greater minerotrophic status, drier hydroperiod, or a seasonally 

variable water table resulting from topographic runoff. Hummocks are usually well developed. 

The medium-height shrub layer is usually well developed (greater than 0.5 m tall), and in some 

examples, it may be more abundant than the tall shrub layer. 

OLIGOTROPHIC – WEAKLY MINEROTROPHIC TYPES (VERY ACIDIC – ACIDIC) 

• Highbush blueberry-mountain holly shrub thicket/sparse woodland (S3S4) 

Vaccinium corymbosum-Nemopanthus shrub thicket/sparse woodland 

This is an oligotrophic to weakly minerotrophic community characterized by a mixture of tall 

and medium height heath shrubs, and usually a sparse canopy of Picea mariana (black spruce), 

Larix laricina (eastern larch), and sometimes Pinus strobus (white pine) or Pinus rigida (pitch 

pine). This community occurs over large areas of perched basins or more commonly as a border 

thicket around more open dwarf heath peatlands, including kettle hole bogs. A mixture of 

northern and more southern or coastal species is characteristic. Tall shrubs average ca. 15% 

cover (range is 1-30%) and usually include Vaccinium corymbosum (highbush blueberry), 

Nemopanthus mucronatus (mountain holly), Lyonia ligustrina (male-berry), and Aronia 

melanocarpa (black chokeberry). Ilex verticillata (winterberry) and forbs indicative of more 

minerotrophic conditions are generally not present. Dwarf and medium-height shrubs are on 

average more abundant (34% cover) than tall shrubs and include Chamaedaphne calyculata 

(leather-leaf), Kalmia angustifolia (sheep laurel), Gaylussacia baccata (black huckleberry), and 


occasionally K. polifolia (bog laurel). Woodwardia virginica (Virginia chain-fern) and Carex 

trisperma var. billingsii (Billing's sedge) are occasional. Sphagnum magellanicum is dominant, 

while S. rubellum is characteristic but less frequent and abundant than in Sphagnum 

rubellum/Vaccinium oxycoccos dwarf heath moss lawns that lack tall shrubs. Sphagnum 

bartlettianum, a species with coastal and southern distributional tendencies, is infrequent. 

This community generally occurs in southern and central New Hampshire, and rarely farther 

north at low elevations (below 1300 ft.). Average pH is 3.9. The medium shrub layer averages 

ca. 0.85 m in height and is therefore taller than that of dwarf heath communities. Peat is 

moderately well decomposed within the upper 0.5 m, and hummock-hollow topography is 

moderately well developed (average hummock height 0.26 m). 

Two variants are apparent: 

1. Rhododendron canadense-Nemopanthus mucronatus-Sphagnum russowii variant: 

This variant is characterized by a much higher frequency and abundance of 

Rhododendron canadense (rhodora) and Sphagnum russowii with little or no Vaccinium 

corymbosum (highbush blueberry). The most frequent tall shrub species are 

Nemopanthus mucronatus (mountain holly) and Viburnum nudum var. cassinoides 

(witherod). Peat is moderately well decomposed within 0.25 m of the surface. Other 

hummock Sphagnum mosses include S. capillifolium and S. fuscum. Sphagnum russowii 

is occasional but more frequent than in the next variant, and S. angustifolium is 

occasional to sometimes abundant. 

2. Vaccinium corymbosum-Gaylussacia baccata-Vaccinium macrocarpon variant: This 

variant has a higher frequency and abundance of Vaccinium corymbosum (highbush 

blueberry) and Gaylussacia baccata (black huckleberry), and Vaccinium macrocarpon 

(large cranberry) occurs in low abundance. Rhododendron canadense (rhodora) and 

Nemopanthus mucronatus (mountain holly) are occasional but not as frequent as in the 

other variant. There is also a higher frequency of dwarfed Picea mariana (

• Montane heath shrub thicket/sparse woodland (S2) 

Montane heath shrub thicket/sparse woodlands are found on mesic to wet-mesic sites on flat 

ridges and slopes near the transition to heath/krummholz. This community occurs in several 

locations in the White Mountains at the transition to subalpine communities and in association 

with Calamagrostis pickeringii/shrub level/sloping fens in the upper Pemigewasset River valley. 

It occurs at elevations ranging from 2500 to 4000 ft. This peatland community is similar to 

subalpine heath snowbanks but is distinguished from them by a lack of subalpine species, a taller 

woodland structure (>2 m), and a robust (0.4-1.5 m tall) shrub layer. Trees in the sparse 

woodland canopy include Picea mariana (black spruce) and/or Picea rubens (red spruce) and 

Abies balsamea (balsam fir). A well developed, medium to tall heath shrub layer is 

characterized by Rhododendron canadense (rhodora), Nemopanthus mucronatus (mountain 

holly), Ledum groenlandicum (Labrador-tea), Kalmia angustifolia (sheep laurel), and Viburnum 

nudum var. cassinoides (witherod). Alnus incana var. americana (speckled alder) is absent or in 

low abundance in this natural community. Soils are shallow peat over bedrock or silty gravel. 

• Montane alder-heath shrub thicket (S1) 

The montane alder-heath shrub thicket community is restricted to the upper East Branch of the 

Pemigewasset River watershed near Shoal and Ethan Pond in the White Mountains at elevations 

above 2400 ft. Structurally, it is dominated by tall shrubs with scattered trees and small openings 

supporting herbaceous plants. Characteristic shrubs include Alnus incana var. americana (speckled 

alder), Rhododendron canadense (rhodora), Nemopanthus mucronatus (mountain holly), and 

Viburnum nudum var. cassinoides (witherod). Other common plants include Ledum groenlandicum 

(Labrador-tea), Vaccinium myrtilloides (velvet-leaf blueberry), Gaultheria hispidula (creeping 

snowberry), Larix laricina (eastern larch), and Picea mariana (black spruce). Scattered herbaceous 

vascular plants found in small openings include Eriophorum virginicum (tawny cotton-grass), 

Drosera rotundifolia (round-leaved sundew), Carex trisperma (three-seeded sedge), Calamagrostis 

pickeringii (Pickering's reed bent-grass)*, Thalictrum pubescens (tall meadow rue), Aster umbellatus 

(umbellated aster), Chelone glabra (turtlehead), Carex intumescens (bladder sedge), and Glyceria 

melicaria (a mannagrass). Sphagnum mosses are abundant. 

Soils are characterized by shallow organics over hydric, cryic, silty gravels. Organic soil 

depths are generally shallower than those underlying the related montane Calamagrostis 

pickeringii/shrub level/sloping fen. Near-surface water pH is 5.0. Hummock and hollow 

topography is moderately developed. 

WEAKLY MINEROTROPHIC – INTERMEDIATE TYPES (ACIDIC – SUBNEUTRAL) 

• Winterberry/cinnamon fern/spruce tall shrub thicket/sparse woodland (S4) 

Ilex verticillata/Osmunda cinnamomea/Picea tall shrub thicket/sparse woodland 

This is a weakly to moderately minerotrophic tall shrub thicket community that occurs in 

central and southern New Hampshire. It is floristically transitional between more northern 


oligotrophic Vaccinium-Nemopanthus tall shrub thickets and more central and southern Ilex 

verticillata (winterberry) thickets and woodlands that lack Picea mariana (black spruce) and 

Larix laricina (eastern larch). This community is characterized by Picea mariana, Larix 

laricina, and various tall, northern shrub species. Acer rubrum (red maple), Ilex verticillata, and 

Osmunda cinnamomea (cinnamon fern) are more typical of the southern communities. Other 

characteristic shrubs include Vaccinium corymbosum (highbush blueberry), Nemopanthus 

mucronatus (mountain holly), Lyonia ligustrina (male-berry), and Viburnum nudum var. 

cassinoides (witherod). The tree layer is sparse (ca. 1-20% cover), and the tall shrub layer is 

moderate to dense (average ca. 40% cover, including tree species in the shrub layer). The 

medium shrub layer is sparse to moderately well developed (1-25% cover, average height 0.85 

m), including Kalmia angustifolia (sheep laurel), Myrica gale (sweet gale), and Gaylussacia 

baccata (black huckleberry). Low shrubs occupy hummocks and include Gaultheria hispidula 

(creeping snowberry), Vaccinium myrtilloides (velvet-leaf blueberry), and Rubus hispidus 

(bristly dewberry). The most prominent herbs are Osmunda cinnamomea (cinnamon fern), 

Smilacina trifolia (three-leaved false Solomon's seal), and Carex trisperma var. trisperma (threeseeded 

sedge). Aster nemoralis (bog aster) and Aster x blakei (Blake’s aster) are occasional. An 

abundant moss cover is characterized by a combination of Sphagnum henryense, S. palustre, S. 

fallax, and S. angustifolium, indicating minerotrophic to weakly minerotrophic conditions. 

This community has an average pH of 4.35. Well decomposed peat occurs near the surface 

(H8 at 20 cm), and hummock and hollow topography is well developed (average hummock 

height 0.32 m, average maximum height 0.50 m). 

• Winterberry/cinnamon fern/Sphagnum fallax tall-medium shrub thicket (S4) 

Ilex verticillata/Osmunda cinnamomea/Sphagnum fallax tall-medium shrub thicket 

This community is weakly minerotrophic and typically occurs in laggs or as an upland border 

zone in southern and central New Hampshire peatlands (below 1000 ft. elevation). Acer rubrum 

(red maple) is always present in low abundance in the sparse, low-tree canopy or tall shrub layer, 

but tall shrubs and variable mixtures of medium shrubs and herbaceous species dominate the 

community. A few examples are dominated by herbs such as Carex canescens (silvery sedge) 

and have little shrub cover. 

Herbaceous species indicative of at least weakly minerotrophic conditions are in low 

abundance but are diagnostic. These include Osmunda cinnamomea (cinnamon fern), Carex 

canescens (silvery sedge), Lysimachia terrestris (swamp candles), Triadenum virginicum (marsh 

St. John’s-wort), Lycopus uniflorus (common water horehound), and Carex stricta (tussock 

sedge; occasionally abundant). Calla palustris (wild calla), Iris versicolor (northern blue flag), 

and Typha latifolia (common cat-tail) are occasional in wet hollows. Tall shrubs are always 

present but vary from ca. 5-40% cover. Characteristic tall shrubs include Vaccinium 

corymbosum (highbush blueberry), Ilex verticillata (winterberry), Lyonia ligustrina (male-berry), 

Nemopanthus mucronatus (mountain holly), Alnus incana (speckled alder), and Aronia 

melanocarpa (black chokeberry). Decodon verticillatus (water willow) is occasionally abundant, 


and Chamaedaphne calyculata (leather-leaf), Kalmia angustifolia (sheep laurel), Gaylussacia 

baccata (black huckleberry) are common. Clethra alnifolia (sweet pepperbush) is occasional in 

coastal examples. Sphagnum fallax (sensu latu) is frequent and usually abundant (=Sphagnum 

fallax (sensu stricta) and S. isoviitae). Sphagnum fimbriatum and S. cuspidatum are frequent, 

while S. henryense, S. recurvum, and S. affine are occasional. The moss Aulocomnium palustre 

is occasional. 

Average pH is 4.4. Peat is well decomposed near the surface (H6 at 0.2 m), and hummockhollow 

topography is well developed (average hummock height is 0.22 m; average maximum 

height is 0.44 m). Medium shrub height averages 0.84 m. 

• Highbush blueberry/sweet gale-meadow-sweet tall-medium shrub thicket (S4) 

Vaccinium corymbosum/Myrica gale-Spiraea alba tall-medium shrub thicket 

This is a weakly to moderately minerotrophic, limnogenous community dominated by 

medium height shrubs (average height 0.90 m) with a sparse to moderate cover of tall shrubs. It 

is found along upland borders and laggs of acidic fens, along sluggish stream borders, and 

sometimes as the dominant fen community in basins that are influenced by upland runoff. This 

community is found primarily at low to mid elevations (below 1500 ft.) in central and southern 

New Hampshire, but it does occur occasionally in the northern part of the state. Myrica gale 

(sweet gale) and Spiraea alba (meadow-sweet) are diagnostic in combination with tall shrubs, 

including various combinations of Vaccinium corymbosum (highbush blueberry), Lyonia 

ligustrina (male-berry), Aronia melanocarpa (black chokeberry), Ilex verticillata (winterberry), 

and Alnus incana (speckled alder). Chamaedaphne calyculata (leather-leaf) is always present in 

low to moderate abundance. Acer rubrum (red maple) is common in low abundance in the tall 

shrub and low tree layers. Carex utriculata (bottle-shaped sedge), Kalmia angustifolia (sheep 

laurel), and Rhododendron canadense (rhodora) are occasional. Bryophyte cover is moderate 

(average ca. 50% cover), with Sphagnum fimbriatum, S. henryense, S. torreyanum, S. flexuosum, 

and S. fallax usually present in some combination. 

Average pH is 4.6. Hummock-hollow topography is well developed (average hummock 

height 0.25 m; average maximum height 0.47 m), and peat is moderately well decomposed near 

the surface (H6 at 0.20 m). Peat depths are often less than 1 m. 

MARSHY PEATLAND-MARGIN COMMUNITIES 

These peatland communities occur adjacent to quiet pond and lake borders, stagnant streams, 

or upland habitats where a minerotrophic influence from upland runoff or open water exists. 

They may be transitional to aquatic beds, emergent marshes, shrub thickets, or upland habitats. 

Some peatland types described elsewhere may occur along pond or upland borders but do not 

contain an abundance of emergent or aquatic marsh species indicative of the two types below. 


• Floating marshy peat mat (S3) 

This community occurs along quiet margins of ponds and lakes or stagnant, slow-moving 

streams on floating, loosely consolidated, thin, well-decomposed peat. It is transitional between 

an emergent marsh/aquatic bed and an open peatland on thicker, more consolidated peat 

landward. Species composition is somewhat variable and may include Nymphaea odorata 

(white water-lily), Nuphar variegata (variegated yellow pond-lily), Eriophorum viridicarinatum 

(green keeled cotton-grass), Eleocharis flavescens var. olivacea (olive-brown spike-rush), 

Eleocharis smallii (Small's spike-rush), Rhynchospora alba (white beak-rush), Drosera 

intermedia (spatulate-leaved sundew), Triadenum virginicum (marsh St. John's-wort), Dulichium 

arundinaceum (three-way sedge), Utricularia spp. (bladderworts), Pontederia cordata (pickerelweed), 

Iris versicolor (northern blue flag), Juncus pelocarpus (mud rush), Hypericum boreale 

(northern St. John's-wort), and other forbs and graminoids. Shrubs are sparse and stunted or 

absent. 

The depth of the floating peat mat ranges from a few to more than 50 cm, and pHs range 

from 4.4-5.7 and are influenced by the close proximity of the peat mat to open water. The mat 

surface is flat with occasional, very low micro-relief and ranges from less than a meter to several 

meters wide. This community occurs throughout New Hampshire. 

• Marshy moat (S4) 

Moats are wetland zones generally found between other peatland communities and adjacent 

upland habitats, typically in southern and central New Hampshire. Moats may vary 

considerably, both within and between sites, in width (less than 1 m to more than 20 m) and in 

duration and frequency of flooding. They may be restricted to basins with significant yearly 

water fluctuations. Moat development likely is related to increased peat decomposition along the 

peatland edge as a result of decreased acidity and dry periods during seasonal water-level 

drawdown. Other peatland communities (e.g., Ilex verticillata/Osmunda cinnamomea/Sphagnum 

fallax tall-medium shrub thicket, Decodon verticillatus/Sphagnum recurvum-S. flexuosum border 

thicket, Sphagnum torreyanum/Vaccinium macrocarpon/Rhynchospora alba moss lawn, and 

Sphagnum cuspidatum/Vaccinium macrocarpon moss lawn) also may occur in moat-locations; 

the type described here differs in the greater prominence of emergent marsh or aquatic species. 

Vegetation is typically poorly to moderately developed, variable in composition, and with a 

number of minerotrophic indicator species. Temporarily to seasonally flooded moat zones 

support most of the shrub and emergent marsh species present. Emergent or aquatic species 

generally absent from other peatland types include Sparganium americanum (lesser bur-reed), 

Glyceria spp. (manna-grass), Scirpus cyperinus (woolly bulrush), Eleocharis smallii (Small's 

spike-rush), Calamagrostis canadensis (blue-joint), Juncus canadensis (Canada rush), and 

Juncus effusus var. solutus (soft rush). In semi-permanently flooded moat zones, several aquatic 

species may be present, including Potamogeton spp. (pondweeds), Brasenia schreberi (water 

shield), Utricularia vulgaris (common bladderwort), Nuphar variegata (variegated yellow pond- 


lily), and Nymphaea odorata (white water-lily). Other characteristic emergent and other species 

also occasional in other peatland communities include Peltandra virginica (arrow-arum), 

Dulichium arundinaceum (three-way sedge), Triadenum virginicum (marsh St. John's-wort), 

Carex canescens (silvery sedge), Carex lasiocarpa var. americana (hairy-fruited sedge), 

Lycopus uniflorus (common water horehound), and Lysimachia terrestris (swamp candles). 

Shrubs may include Cephalanthus occidentalis (buttonbush), Vaccinium corymbosum (highbush 

blueberry), Ilex verticillata (winterberry), Decodon verticillatus (water willow), Chamaedaphne 

calyculata (leather-leaf), Spiraea alba var. latifolia (eastern meadow-sweet), Aronia 

melanocarpa (black chokeberry), and Myrica gale (sweet gale). Sphagnum species may be 

absent or when present, unconsolidated and often characterized by Sphagnum cuspidatum and 

other Sphagna found in “soupy” conditions. Moss species that may be found on woody stem 

bases and elsewhere in the moat include Callicladium haldanianum, Hypnum pallescens, and 

Aulocomnium palustre. 

Soils are typically relatively shallow, well-decomposed peat. Because the moat is located 

where surface water runoff enters the peatland, nutrient availability and pHs are generally higher 

in the moat than in areas closer to the peatland center. 


FORESTED SWAMPS AND FLOODPLAIN FORESTS 

SATURATED/SEASONALLY FLOODED BASIN SWAMPS 

These swamps are very poorly and poorly drained, occur on shallow to deep muck and peat 

soils (histosols, histic epipedons, or mineral histic soils), and have little or no streambank 

overflow or seepage influence. 

MUCK AND PEAT SWAMPS 

MODERATELY SHALLOW (10-20 CM) TO DEEP (>40 CM) 

• Red maple/Sphagnum saturated basin swamp (S4) 

Acer rubrum/Vaccinium-Ilex/Osmunda/Sphagnum basin swamp 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This is a common type of “red maple swamp” 

on poorly to very poorly drained peat soils of depressions with minimal influence of groundwater 

or seasonal overbank stream flow. There are typically no perennial streams running into or 

through the swamps, although the basins are influenced by seasonal subsurface and ephemeral 

runoff from surrounding uplands. They occur in perched basins in till landscapes or other low, 

flat areas with small watersheds of typically 1/4 to 1 mile square or less. Hummock and hollow 

topography is well developed. 

SOILS/GEOLOGY/HYDROLOGY: Soils are acidic, nutrient-poor, very poorly drained histosols (deep 

peat or muck) or poorly to very poorly drained histic epipedons (O horizons are generally

(wintergreen). Sphagnum mosses are usually dominant or abundant in hollows and on lower sides 

of hummocks and include Sphagnum fallax, S. girgensohnii, and S. papillosum, among others. 

Wetter hollows in somewhat open swamps may have a greater abundance of species such as Carex 

canescens (silvery sedge) and Calla palustris (wild calla). 

Examples with considerable black gum are treated as a separate type, but have many 

similarities to the typic variant. Although more data are needed to understand variation among 

these swamps, one major gradient within the type may be differences in hydroperiod. This 

apparent variation is represented by the two broad variants described below. 

1. Typic saturated variant: This includes classic, stagnant, low diversity red 

maple/cinnamon fern/Sphagnum basin swamps as described above. These swamps at the 

“boggy” end of the gradient are more stagnant with very little through-flow, saturated 

conditions, and relatively little seasonal fluctuation. These often occur in basins with no 

inlets or outlets or in stagnant headwater sections of drained basins in central or isolated 

“back ends” of swamp systems. The shrub and herb layer may be denser on wetter sites 

with lower tree cover (30-60%) than on somewhat drier sites with denser tree cover. This 

variant is very similar to the black gum red maple swamp described elsewhere. 

2. Seasonally saturated and seasonally flooded variants: These variants include basin 

swamps that appear to have somewhat greater influence of through-flow from upland 

runoff or have a more broadly fluctuating seasonal water table that results in less poorly 

drained situations. However, this fluctuation is not as substantial as in streamside 

swamps or in those with pronounced groundwater influence. These basin swamps may 

have a tendency to occur closer to upland margins or in slightly more well drained basins 

with larger watersheds and may have a more diverse herb layer. Another expression of 

this variant has a significant component of Carex lacustris (lake sedge), a robust and 

rhizomatous sedge that reaches its best development in more minerotrophic wetlands. 

Lake sedge may reach 30% or more cover, but the vegetation may otherwise be quite 

similar to other stagnant basin swamps. In contrast, seasonally flooded or seepage 

swamps with abundant lake sedge tend to have no or little Sphagnum development, minor 

hummock development, and shallower peat (see description elsewhere). Known 

examples have moderate organic horizon accumulations of less than 40 cm overlying silt 

or silt loam mineral horizons (Bloody Brook (Exeter)). 

This variant includes seasonally saturated swamps dominated by red maple and 

hemlock in the canopy and subcanopy, although they may deserve to be recognized as a 

distinct type. In general, organic horizons may tend to be shallower, herb and shrub 

density lower, and Sphagnum moss less abundant than in the typic variant. Shade 

produced by the hemlock component may have some influence on the density and 

diversity of the herb and shrub layers. Upland plants such as Betula lenta (black birch), 

Quercus rubra (red oak), Gaylussacia baccata (black huckleberry), and Maianthemum 

canadense (wild-lily-of-the-valley) may be more abundant on low to medium sized 


hummocks and island inclusions. This variant is transitional to black gum swamps with 

considerable hemlock. More data are needed on these types. 

DISTRIBUTION: Found throughout central and southern New Hampshire. 

COMMENTS: Fairly distinct from seepage and streamside wetlands, but variable and worthy of 

further study in the region to clarify community differences. 

GOOD EXAMPLES: In Coastal Lowlands Ecoregion: LaRoche Brook vicinity (Durham); Bloody 

Brook/Norris Brook headwaters (Exeter). 


• Atlantic white cedar-yellow birch/sweet pepperbush swamp (S2) 

Chamaecyparis thyoides-Betula alleghaniensis/Clethra alnifolia swamp (North Coastal NE or 

Gulf of Maine type) 

This Atlantic white cedar community type occurs in near-coastal areas and is usually 

characterized by the presence of the indicator species Clethra alnifolia (sweet pepperbush) and 

Betula alleghaniensis (yellow birch), and the lack of boreal or marshy indicator species of the 

other types (based on Sperduto and Ritter (1994) and Motzkin (1991)). Ilex verticillata (swamp 

winterberry), Vaccinium corymbosum (highbush blueberry), Acer rubrum (red maple), Sphagnum 

spp. (Sphagnum moss), Pinus strobus (white pine), and Maianthemum canadense (wild-lily-of-thevalley) 

are abundant or frequent. Tsuga canadensis (hemlock) was abundant at a few sites but 

absent at others. Frequent hummock species include Aralia nudicaulis (wild sarsaparilla), 

Trientalis borealis (starflower), and mosses. Nemopanthus mucronatus (mountain holly) is 

frequent and sometimes abundant. Species generally absent from the seasonally flooded type but 

occasional here include Carex trisperma (three-seeded sedge) and Kalmia angustifolia (sheep 

laurel). Thelypteris simulata (Massachusetts fern) appears to be restricted to this type. The rare 

coastal plain species Carex seorsa (separated sedge) and Carex striata var. brevis (Walter's sedge) 

occur in some examples. Rhododendron viscosum is not present in this type, but does occur in the 

boreal type and sparsely in the Rhododendron maximum (great laurel) variant described from a 

Merrimack River valley site (absent from seacoast). 

This type is most similar to Motzkin's (1991) mixed hemlock-Atlantic white cedar-red mapleyellow 

birch type, but appears to differ by Tsuga canadensis (hemlock) being less constant or 

frequent and the lack of Clintonia borealis (blue-bead lily) that he notes. Motzkin also notes that 

there is "noticeably little" Vaccinium corymbosum (highbush blueberry) and Rhododendron 

canadense (rhodora) in Massachusetts examples; in New Hampshire examples the latter is indeed 

sparse whereas the former usually comprises 1-10% of the shrub canopy, and occasionally more. 

This is not noticeably different than highbush blueberry amounts in most New Hampshire cedar 

swamps. Although this type has some clear and occasionally strong indicators of southern New 

England coastal swamp habitats, it differs from Motzkin's "Coastal Atlantic white cedar type" by 

the lack of Leucothoe racemosa (fetter-bush), Rhododendron viscosum (swamp azalea), 

Woodwardia areolata (netted chain fern) and Ilex glabra (inkberry). For this reason the name 


“North coastal” or Gulf of Maine may be used to distinguish the New Hampshire “coastal” type 

from Motzkin’s “coastal” type. It is apparently similar to Reshke's (1990) "Inland Atlantic white 

cedar swamp" and the "Cedar/hemlock" type reported by Karlin from New Jersey (1988). 

The pH ranges from 4.0 to 5.1 (average 4.5, n=11). Elevation ranges from 20-350 ft. 

Some examples of this type may be transitional to the cedar bog type Motzkin (1991) 

describes, although not enough data are available at this time to recognize it in New Hampshire. 

Cedar was observed on floating mats and other bog or shrubby acidic fen habitats and along their 

borders, but these open peatland habitats were not sampled. Cedar generally formed a sparse 

canopy in these situations except for a narrow transition zone of dense cedar and shrubs between 

the bog/fen and adjacent cedar swamp proper. Bogs and fens with cedar as a minor component 

are not considered distinct types, but rather variants of more broadly defined open peatland 

communities as treated by Rawinski (1984) or Sperduto (1994a). 

• Boreal Atlantic white cedar swamp (S1) 

Chamaecyparis thyoides-Picea rubens/Clintonia borealis swamp 

This type differs from the coastal and seasonally flooded types by the absence of certain 

coastal or southern species such as Clethra alnifolia (sweet pepperbush), Symplocarpus foetidus 

(skunk cabbage), Thelypteris simulata (Massachusetts fern) and by the presence of several more 

northern or boreal species. Picea rubens (red spruce) is abundant at most sites, along with 

frequent Clintonia borealis (blue-bead lily), and Gaultheria hispidula (creeping snowberry). 

Other less frequent but reasonably diagnostic species include Cornus canadensis (bunchberry), 

Abies balsamea (balsam fir), Larix laricina (eastern larch), Picea mariana (black spruce) and 

Gaylussacia baccata (black huckleberry). Carex trisperma (three-seeded sedge) and Kalmia 

angustifolia (sheep laurel) are frequent or abundant. Tsuga canadensis (hemlock) is only 

occasionally present but may form locally significant cover. 

An interesting aspect of the Lovering Mill swamp was the abundance of Rhododendron 

viscosum (swamp azalea), typically a more southern species. This location and the Shed Brook 

site are the northern-most locations for this species in New Hampshire. This was also the only 

community type where Quercus rubra (red oak) were observed beyond the seedling stage. 

At the Cooper Cedar Woods in New Durham there is a general paucity of red spruce 

indicative of this type but larch, balsam fir, and bluebead lily are locally abundant in addition to 

other boreal indicators. The site is at 520 ft. elevation and has the highest latitude of any New 

Hampshire Atlantic white cedar location, although it is intermediate in distance to coast (36 

miles). The other examples of this type are all in the western part of the state. Several plots 

from the Bakie, Barrington and Portsmouth cedar swamps have small amounts of either spruce, 

Carex trisperma (three-seeded sedge) and/or Kalmia angustifolia (sheep laurel) which tends to 

align them to this type, but they lack a number of the other associates mentioned above and are 

best considered as variation within the north coastal type. 


The pH ranges from 3.4-4.8 (average 4.1, n=12). Western swamps ranged in elevation from 

890-1040 ft.; Cooper Cedar Woods is at 520 ft. 

This is most similar to the spruce-hemlock-Atlantic white cedar type described for 

Massachusetts by Motzkin (1991). Other high elevation stations for cedar not sampled 

correspond to the seasonally flooded type, but are simply considered small populations of cedar, 

not examples of one of the above types, although cedar may have been abundant at one time. 

This type is considered as a distinct type in New Hampshire not simply a variant form of more 

broad-ranging boreal swamp forests. Motzkin (1991) treats certain Massachusetts swamps with 

cedar as boreal swamp variants. At the larger New Hampshire sites, Atlantic white cedar is a 

major component of the canopy over large areas and is known to have been present for 4,000 

years at one site (Belling 1977), implying that Atlantic white cedar is not an ephemeral 

constituent. 

• Black spruce-larch/heath/Sphagnum basin swamp (G5 S3) 

Picea mariana-Larix laricina/Ledum-Rhododendron canadense/Sphagnum saturated forest/ woodland 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This is a forest or woodland swamp found on 

nutrient-poor, moderately deep to deep peat soils in stagnant basins or stagnant areas within 

other wetland complexes. It is dominated by Picea mariana (black spruce) and/or Larix laricina 

(eastern larch) depending on the nutrient status and degree of saturation. Classic “bog forests” 

that surround open bogs and fens or dominate forested basins without open peatlands are 

included here. This type differs from red spruce swamps by a shift to black spruce and/or larch 

in the tree canopy, usually a greater abundance or dominance of dwarf heath shrubs, lower 

abundance and frequency of Osmunda cinnamomea (cinnamon fern), and generally deeper, 

wetter, and more nutrient-poor peat soils. 

Black spruce and larch are both relatively intolerant of shade and tolerant of saturated 

conditions. Both can adjust to changing water conditions by producing adventitious roots from 

the stem, layering from branches, and to some extent by root sprouting (Fowells 1965; Montague 

and Givnish 1996). Overall, black spruce is a bit more shade tolerant than larch and usually 

dominates on more oligotrophic peatlands of low pH (3.0-4.0), where it grows taller and faster 

than larch (Montague and Givnish 1996). Larch is more prominent on sites with higher pH 

(>4.5) and mineral availability (Bares and Wali 1979), where it grows taller and faster than black 

spruce (Montague and Givnish 1996). This relates well to the general ecological principal that 

coniferous evergreen species have a competitive advantage on low nutrient sites because of the 

higher nutrient use efficiency afforded by evergreen foliage. 

Tree canopies vary from as little as 2-3 m height to more than 15 m and probably depend to a 

large extent on nutrient status and degree of inundation, as well as time since disturbance. As the 

canopy thins and transitions to open peatland types, the height usually decreases. There is no 

explicit evidence of fire history in New Hampshire examples, but boreal counterparts in Canada 

probably have a more frequent fire regime. Black spruce can exceed 250 years of age in New 


Hampshire swamps (e.g., Cypress Brook) but are more typically younger, probably due in part to 

cutting histories. 

SOILS/GEOLOGY/HYDROLOGY: Soils are typically moderate to deep (>0.5 m), nutrient poor 

(oligotrophic) peat soils. Some black spruce sites have shallower peat soils, where they may 

tend to have a greater abundance of red spruce and balsam fir (based on at least 2-3 known 

examples). Most sites are saturated, with the water table at or near the surface most of the year. 

They range from having little to moderate influence of acidic groundwater flow and upland 

runoff and usually no regular influence of seasonal streambank overflow. 

CHARACTERISTIC VEGETATION: Black spruce and/or larch form a discontinuous canopy cover of 

25% to >80%, usually with a moderate to dense dwarf heath shrub layer, a variable tall shrub 

layer, an abundance of Carex trisperma var. trisperma (three-seeded sedge), and a low to modest 

cover of other herbs. Tall shrubs include Nemopanthus mucronatus (mountain holly), Viburnum 

nudum var. cassinoides (witherod), Lyonia ligustrina (maleberry), and Aronia melanocarpa 

(black chokeberry). Dwarf heath shrubs include Ledum groenlandicum (Labrador tea), Kalmia 

angustifolia (sheep laurel), Rhododendron canadense (rhodora), Vaccinium myrtilloides (velvetleaved 

blueberry), Chamaedaphne calyculata (leather-leaf), Kalmia polifolia (bog laurel), 

Vaccinium oxycoccos (small cranberry), and Gaultheria hispidula (creeping snowberry). 

Herbaceous plants include peatland-restricted species such as Smilacina trifolia (three-leaved 

Solomon’s-seal) and Sarracenia purpurea (pitcher plant), as well as other northern plants 

including Coptis groenlandica (goldthread) and Cornus canadensis (bunchberry). Osmunda 

cinnamomea (cinnamon fern) is occasional. A diversity of Sphagnum moss species forms a 

ubiquitous understory. 

The following variation is recognizable among New Hampshire examples and deserves 

further study: 

1. Typic black spruce/dwarf heath woodland variant: This includes most examples 

north of and including the White Mountain region, as described above. 

2. Black spruce-larch/moss forest variant: This corresponds to examples with a more 

closed canopy, a less well developed heath layer, a sparse to moderate tall shrub layer, 

and a well developed moss layer. 

3. Larch woodland variant: Larch becomes more prominent on more minerotrophic sites. 

The dwarf heath layer may be less well developed than on classic nutrient-poor black 

spruce sites, although more field data are needed to substantiate patterns. 

4. Southern highbush blueberry/huckleberry variant: Examples in southern and central 

New Hampshire may have species that reach their northern limit in central New England, 

including Gaylussacia baccata (black huckleberry) and Vaccinium corymbosum 

(highbush blueberry). 

DISTRIBUTION: Moderately large examples are found only in the six northernmost subsections of 

the state, although small disjunct examples are associated with open peatlands or stagnant basins 


in the Coastal Plain and Coastal Lowland subsections (may be absent from Connecticut River 

subsection). Elevations mostly range from 1000-3500 ft., with small examples in the southern 

part of the state occurring as low as ca. 200 ft. 

COMMENTS: Peatlands with a lower abundance of trees are classified as bogs or fens (n=8+). 

GOOD EXAMPLES: Cypress Brook (Beans Purchase); several sites in the Connecticut Lakes/Back 

Pond vicinity (Pittsburg); Norton Pool (Pittsburg); Stearns Branch vicinity (Success); Trudeau 

Road vicinity (Bethlehem); disjunct southern variant at Camp Carpenter (Londonderry). 

SOURCES: NH Heritage field surveys; Montague and Givnish (1996). 

• Black gum-red maple basin swamp (S1S2) 

Nyssa sylvatica – Acer rubrum/Ilex verticillata/Sphagnum 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: Black gum–red maple basin swamps are very 

similar in vegetation, soils, and hydrology to red maple/Sphagnum saturated basin swamps 

(Sperduto 1997a). A principal distinction between these communities is the codominance of 

black gum with red maple in the canopy of black gum–red maple basin swamps. These swamps 

typically occur in perched upland till basins with watersheds smaller than one square mile. No 

vascular species are uniquely diagnostic of black gum swamps compared to red maple basin 

swamps, but species typical of acidic, relatively stagnant conditions are prevalent. Black gum– 

red maple basin swamps are highly variable in structure and composition, likely resulting in part 

from variability in hydroperiod and nutrient availability. These swamps vary from forest (greater 

than 60% tree cover) to sparse woodland (10 to 25% tree cover), with corresponding increases in 

the density of the shrub layer in woodland and sparse woodland examples. Historical logging 

activities may also have influenced the structure and composition of these swamps, and 

additional research on stand history is needed to clarify the relationships between land use 

history and current vegetation. 

SOILS/GEOLOGY/HYDROLOGY: Soils are typically organic in nature, including acidic, nutrientpoor, 

very poorly drained histosols (deep peat or muck) or poorly to very poorly drained histic 

epipedons. Peat is typically well decomposed near the surface, and pHs average approximately 

4.4 (range: 3.7–5.3). Hummocks are well developed and average approximately 0.4 m high. As 

in other basin swamps, black gum–red maple basin swamps have relatively little evidence of 

seepage or surface water flow. Examples in lakeside settings may be influenced somewhat by 

surface flow, but water sources are generally restricted to precipitation, seasonal subsurface flow, 

and ephemeral runoff from surrounding uplands. Many of these swamps have stagnant outlet 

streams but no perennial inlets or streams running through them; others have neither inlets nor 

outlets. 

CHARACTERISTIC VEGETATION: In the majority of black gum–red maple basin swamps, Nyssa 

sylvatica (black gum) and Acer rubrum (red maple) dominate the tree canopy, with varying but 

smaller contributions by other hardwood and softwood species. Vaccinium corymbosum (highbush 

blueberry) and Ilex verticillata (winterberry) are typically the primary dominants in the shrub 


layer, with a variable component of other tall and medium-height shrub species. Osmunda 

cinnamomea (cinnamon fern) is generally abundant in the herbaceous layer, which consists of a 

combination of some species indicative of moist, acidic conditions (particularly in hollows) and 

others characteristic of drier habitats (typically on hummocks). Sphagnum mosses often form a 

patchy to dense layer, particularly in hollows and on the lower sides of hummocks. The species 

composition of three variants is described in detail: 

1. Boggy woodland/tall shrub thicket variant (Nyssa sylvatica-Acer rubrum/Vaccinium 

corymbosum-Ilex verticillata): This variant predominantly consists of woodlands or 

sparse woodlands. A mixture of Nyssa sylvatica (black gum) and Acer rubrum (red 

maple) dominates in the tree canopy; softwood species, such as Picea rubens (red spruce) 

and Tsuga canadensis (hemlock), may be present in low abundance in the canopy but are 

more likely to occur in the understory. The tall shrub layer is correspondingly moderate 

to very dense, the herbaceous layer is sparse to moderate, and Sphagnum mosses form a 

moderate to dense, sometimes patchy ground cover. 

The shrub layer is generally dominated by tall shrub species. Vaccinium corymbosum 

(highbush blueberry) and Ilex verticillata (winterberry) typically codominate, but 

Nemopanthus mucronatus (mountain holly) may also be abundant. Other shrub species 

may include Ilex laevigata (smooth winterberry), Cephalanthus occidentalis 

(buttonbush), Aronia arbutifolia (red chokeberry), and the short shrub species Kalmia 

angustifolia (sheep laurel). 

While the herbaceous layer is generally not dense, Carex canescens (silvery sedge), 

Carex trisperma var. trisperma (three-seeded sedge), and Osmunda cinnamomea 

(cinnamon fern) are frequently present in low to moderate abundance. Relatively 

frequent species include Coptis trifolia var. groenlandica (goldthread), Osmunda regalis 

var. spectabilis (royal fern), Lysimachia terrestris (swamp candles), Lycopus uniflorus 

(common water horehound), and Dulichium arundinaceum (three-way sedge). The 

upland species Trientalis borealis (starflower) and Aralia nudicaulis (wild sarsaparilla) 

occur frequently but in low abundance on drier hummocks. 

Sphagnum mosses occur both on hummocks and in hollows but predominate in the 

wetter hollows of this variant. Sphagnum magellanicum is the most frequent and 

abundant Sphagnum species. S. torreyanum, a predominantly aquatic, coastal plain 

species, is locally dominant in hollows. 

Sites of this variant type appear to be wetter on average than other examples, based 

on the frequency of hydrophytic species such as Sphagnum torreyanum and Carex 

canescens. Lakeside occurrences of black gum–red maple basin swamp typically fall 

within this variant. The woodland/sparse woodland structure characteristic of these 

swamps may result in part from a longer hydroperiod than in other swamps; however, 

logging history should also be investigated for its potential influence on composition and 

structure, as some apparent examples may be successional to a more forested state. 


2. Boggy forest/woodland variant (Nyssa sylvatica-Acer rubrum-Picea rubens-Pinus 

strobus/Sphagnum): The forest or woodland tree canopy of this variant is dominated by a 

variable mixture of Nyssa sylvatica (black gum) and Acer rubrum (red maple), frequently 

with a component of Picea rubens (red spruce) and/or Pinus strobus (white pine) in the 

canopy and/or subcanopy. Tsuga canadensis (hemlock) and Betula alleghaniensis 

(yellow birch) are typically restricted to the understory. The shrub and herbaceous layers 

are of moderate density on average but are highly variable, and Sphagnum mosses are 

more abundant on average than in other black gum swamps. The Sphagnum species that 

occur in this variant tend to be indicative of more acidic, nutrient-poor conditions than 

those of the hemlock forest/woodland variant, giving examples a more boggy character. 

In the shrub layer, Vaccinium corymbosum (highbush blueberry) and Ilex verticillata 

(winterberry) dominate; total cover ranges from low to high, but abundance of these 

species is lower on average than that of the boggy woodland/tall shrub thicket variant. 

Viburnum nudum var. cassinoides (witherod) is typically present in low abundance, as are 

the short shrub species Gaultheria procumbens (wintergreen), Gaultheria hispidula 

(creeping snowberry), and Cornus canadensis (bunchberry). Other relatively frequent 

shrub species include Nemopanthus mucronatus (mountain holly), Lyonia ligustrina 

(male-berry), and Kalmia angustifolia (sheep laurel). Ilex laevigata (smooth winterberry) 

and Cephalanthus occidentalis (buttonbush) typically are not present. 

Density of the herbaceous layer is moderate on average but variable. Osmunda 

cinnamomea (cinnamon fern) typically dominates, while Coptis trifolia var. groenlandica 

(goldthread) and Carex trisperma var. trisperma (three-seeded sedge) are generally 

present in low abundance. Carex canescens (silvery sedge) may occur in low abundance 

in wetter hollows and Trientalis borealis (starflower) on drier hummocks. Sarracenia 

purpurea (pitcher-plant) occurs only occasionally, but its presence helps distinguish this 

variant from the hemlock forest/woodland variant described below. 

Sphagnum mosses typically form a relatively dense carpet dominated by one or more 

species, including Sphagnum fallax, S. angustifolium, and/or S. magellanicum. S. 

magellanicum tends to be a generalist species of many acidic, somewhat open, northern 

peatlands. S. angustifolium is characteristic of open or sparsely wooded oligotrophic to 

minerotrophic peatlands, while S. fallax is indicative of oligotrophic to weakly 

minerotrophic conditions and is characteristic of open or wooded peatlands. 

3. Hemlock forest/woodland variant (Nyssa sylvatica – Acer rubrum – Tsuga canadensis): 

This variant predominantly consists of forests/woodlands dominated by a mixture of 

Nyssa sylvatica (black gum) and Acer rubrum (red maple), often with a strong Tsuga 

canadensis (hemlock) component in the tree canopy and/or subcanopy. Betula 

alleghaniensis (yellow birch), and Pinus strobus (white pine) are typical in the 

understory. While variable, the shrub layer is sparser on average in this variant. 


Sphagnum layers are generally of moderate density. The Sphagnum species that 

occur in this variant suggest slightly more minerotrophic conditions than are present in 

other black gum swamps (Andrus 1980). 

In the shrub layer, Vaccinium corymbosum (highbush blueberry) and Ilex verticillata 

(winterberry) dominate as in the other variants, but total cover is on average fairly low to 

moderate. Other shrub species that occur with some frequency in relatively low 

abundance include Nemopanthus mucronatus (mountain holly), Aronia arbutifolia (red 

chokeberry), and the short shrub species Gaultheria procumbens (wintergreen). 

Total cover in the herbaceous layer generally ranges from low to moderate. Osmunda 

cinnamomea (cinnamon fern) is generally abundant, and Coptis trifolia var. groenlandica 

(goldthread) is typically present in low to moderate abundance. Species that occur 

frequently in low abundance include royal fern, Carex trisperma var. trisperma (threeseeded 

sedge), Aralia nudicaulis (wild sarsaparilla), and Maianthemum canadense 

(Canada mayflower). 

Total cover by bryophyte species is variable but typically ranges from low to 

moderate. Each of the several species of Sphagnum moss in this variant occurs with low 

frequency; considered as a group, however, several of these species are indicative of 

slightly more minerotrophic conditions than are present in the other black gum swamps. 

These minerotrophic indicator species (Andrus 1980) include Sphagnum flexuosum, S. 

affine, S. centrale, S. henryense, S. fimbriatum, S. palustre, and S. recurvum. S. fallax 

tends to occur in weakly minerotrophic conditions. Other Sphagnum species in this 

variant include S. angustifolium, S. magellanicum, S. torreyanum, and S. cuspidatum. In 

addition to the Sphagnum species, other bryophytes are also more frequent. 

Moisture conditions appear to be highly variable. Conditions range from relatively 

dry, with a high frequency of Mitchella repens (partridge-berry), to fairly wet, 

characterized by occurrences of species such as Carex canescens (silvery sedge), 

Thelypteris palustris var. pubescens (marsh fern), and Glyceria canadensis (rattlesnake 

manna-grass). Sphagnum species indicative of slightly more minerotrophic conditions 

are present across this range of moisture levels. Additional minerotrophic indicators that 

occur in this variant include Osmunda regalis var. spectabilis (royal fern – relatively 

frequent), Chelone glabra (white turtlehead – occasional), and Fraxinus nigra (black ash 

– occasional). 

4. Mountain laurel variant (Nyssa sylvatica – Acer rubrum – Kalmia latifolia): Three 

plots from the southwestern portion of the state contained a significant amount of Kalmia 

latifolia (mountain laurel); however, these plots did not emerge as a distinct group during 

the TWINSPAN analysis of the releve plot data. The dominance of mountain laurel in 

these swamps, in additional examples in the state that were not sampled, and in other 

swamps farther south in Massachusetts (Zebryk 1990), may indicate the existence of a 

distinct floristic association worthy of further research. 


MINERAL SOIL SWAMPS 

• Swamp white oak basin swamp (S1) 

Quercus bicolor-Acer rubrum/Sphagnum basin swamp 

Swamp white oak basin swamps are similar to both red maple basin swamps and swamp white 

oak floodplain forests in several respects (based on NH Heritage field surveys and Nichols and 

Sperduto (1997)). The primary difference with floodplain forests is the presence of low to 

moderate hummocks, moderate to abundant amounts of Sphagnum moss, the lack of several 

floodplain plant associates, and the presence of typical basin swamp species. They differ from red 

maple swamps primarily by the abundance of swamp white oak and association with silt loam or 

silt mineral soils, and restriction to the coastal plain lowlands of south eastern New Hampshire. 

Species absent or less abundant in swamp white oak basin swamps compared to floodplains 

include Carpinus caroliniana (musclewood), Cornus amomum (silky dogwood), Ulmus 

americana (American elm), Cinna arundinacea (wood reed), Athyrium filix-femina (lady fern), 

and Onoclea sensibilis (sensitive fern). Species that are more abundant or frequent in swamp 

white oak basin swamps include Osmunda cinnamomea (cinnamon fern), Vaccinium 

corymbosum (highbush blueberry), and Kalmia angustifolia (sheep laurel). Compared to red 

maple basin swamps, swamp white oak swamps appear to have poorly drained mineral histic 

soils that are seasonally saturated or seasonally flooded with very little or a shallow organic 

horizon (up to 5 cm), modest amounts of Sphagnum (1-65%), a relatively sparse herb layer (less 

than 10-15% cover), and a moderate to dense shrub layer. The species composition is similar to 

red maple basins (see this description), with some suggestion of more enriched soil conditions 

imparted by the silty mineral soils by occasional musclewood, elm, arrow-wood, and poison ivy. 

Good examples occur in the Pickpocket vicinity (Exeter) and Stratham Hill vicinity (Stratham). 

SEEPAGE SWAMPS AND MIXED-HYDROLOGY SWAMPS 

(SATURATED, SEASONALLY SATURATED, OR SEASONALLY FLOODED) 

This group of communities includes very poorly to poorly drained seasonally saturated to 

saturated seepage swamps and mixed-hydrology swamps (those with groundwater influence and 

seasonal flooding associated with drainages and runoff). 

WEAKLY ACIDIC TO INTERMEDIATE/CIRCUMNEUTRAL SWAMP FORESTS AND WOODLANDS 

• Red maple-black ash/swamp saxifrage seepage swamp (S2) 

Acer-Fraxinus nigra/Saxifraga pensylvanica seepage swamp 

This is a classic type of seepage swamp with plants indicative of seepage and/or enriched 

conditions readily evident. These swamps are typically found along borders of larger swamp 

systems, in very slightly sloped wetlands where groundwater discharge and/or subsurface upland 

runoff influence the rooting zone of the swamp, or where groundwater discharge in flat basins is 

pronounced or influenced by intermediate/basic bedrock or soils. Soils are typically poorly to 


very poorly drained mineral histic or histic epipedons (shallow muck or peat over grayish or 

gleyed subsoil). Silt loam and silt soils of marine origin typically underlie these swamps in the 

seacoast region (e.g., Buxton or Scitico silt loams), or other soils with higher base-cation status. 

The tree canopy is dominated by red maple with lesser quantities of Fraxinus nigra (black 

ash), Fraxinus americana (white ash), Betula alleghaniensis (yellow birch), and occasionally Tilia 

americana (basswood). A diverse assemblage of herbaceous and moss species may be present 

(e.g., Mnium spp.) although Sphagnum is typically sparse or absent. Seepage indicators such as 

Saxifraga pensylvanica (swamp saxifrage), Geum rivale (water avens), Caltha palustris (marsh 

marigold), Hydrocotyle americanum (water pennywort), Lindera benzoin (spicebush), and Senecio 

robbinsii (Robbins ragwort) are often present. Other typically abundant herbs and shrubs include 

Onoclea sensibilis (sensitive fern), Toxicodendron radicans (poison ivy), Viola spp. (violets), 

Impatiens capensis (jewelweed), Alnus rugosa (speckled alder), and Cornus stolonifera (red osier 

dogwood). Good examples occur at College Woods (Durham) and Shaws Pond. 

• Red maple/lake sedge streamside/seepage swamp (S3) 

Acer rubrum/Carex lacustris streamside/seepage swamp 

Red maple dominates this community, typically comprising a moderate woodland overstory 

structure (25-60 %) accompanied by a dense, tall layer of Carex lacustris (lake sedge). This 

sedge reaches its best development on minerotrophic situations such as seasonally flooded 

streamsides and/or seepage swamps. Sphagnum spp. (Sphagnum moss) are typically absent or 

not abundant in these swamps. Some of these swamps are probably successional from marsh 

situations. Carex stricta (tussock sedge) and Calamagrostis canadensis (blue-joint) are common 

associates and in some cases are quite abundant. Soils in areas sampled are poorly to very poorly 

drained with shallow fibric organic horizons (

• Northern hardwood-black ash-conifer seepage swamp (S2) 

Betula alleghaniensis-Fraxinus nigra-Abies/Geum rivale-Onoclea saturated swamp forest/woodland 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This community is a type of boreal seepage 

swamp with weakly acidic to intermediate pH, shallow peat or mineral soils, with a diverse 

overstory and lush understory composition. A hardwood-conifer mix is typical, although some 

examples have a prominence of one or the other. Although it shares numerous species with the 

red spruce-hardwood/violet variant of the red spruce swamp community, several species 

differentiate this more nutrient rich type. It occupies seepage and/or upland runoff-influenced 

areas including gently sloping hillsides, drainage headwater areas, minerotrophic upland margins 

of streamside or basin swamps and local discharge areas within other swamp types. Hummocks 

tend to be either modest in size (ca. 0.3 m (1 ft.) tall) or are occasionally absent, particularly in 

sloped examples. There is often a gentle but discernable slope to these wetlands. 

Fraxinus nigra (black ash) is characteristic and may occur in nearly pure stands, although it is 

not always abundant or dominant. Although it does not grow as fast as red maple or American 

elm, it’s ability to stump sprout (Fowells 1965) may be an important reproductive strategy in 

response to disturbance in some situations (blowdown, pathogens, or cutting). Although red maple 

also stump sprouts prolifically, black ash may have the advantage in boreal climates. It is fairly 

long-lived (>250 years), can achieve 24 m (80 ft.) in height, and exceed ca. 50 cm (20 in.) diameter 

in exceptional circumstances (Engstrom, NH Heritage field survey, 1995). Most examples are 

fairly small (1-10 acres), although some examples in peatland basins probably exceed 40-50 acres. 

SOILS/GEOLOGY/HYDROLOGY: This is a moderately rich swamp type (mesotrophic) influenced to 

some degree by groundwater seepage and/or near-surface upland runoff, and concentrated in 

northern regions of the state where surficial deposits of intermediate to base rich composition are 

more prevalent. Surface water pHs range from 5.2-6.3 (average=5.8, standard deviation=0.37) 

and conductivity measures range from 20-70 uS (average=36, n=7). Perennially saturated soils 

are typical and surface rivulets and springs are occasionally apparent. Groundwater flowthrough 

is presumably greater than in black spruce/larch peatlands and the amplitude of seasonal 

water level fluctuation and influence of overbank flow is probably considerably less than many 

seasonally flooded streamside swamps. As such, standing water is not likely to persist for long 

(as in some basin swamps), although water is presumably relatively close to the surface much of 

the year. Peat or muck horizons generally consist of well decomposed organic matter and are 

very shallow to absent in some examples, particularly on slopes with gray (gleyed) silty or sandy 

mineral soil. Examples in flat peatland basins have moderately deep peats, averaging 127 cm 

(n=7 sites; range=70-265 cm), and are often mottled near the surface (mineral histic, histic 

epipedons, and shallow histosols). 

CHARACTERISTIC VEGETATION: The most abundant and constant species in the tree canopy 

consist of various combinations of black ash, Betula alleghaniensis (yellow birch), Abies 

balsamea (balsam fir), and Picea rubens (red spruce). Other frequent species include Thuja 

occidentalis (northern white cedar), Acer rubrum (red maple), Picea glauca (white spruce), 

Populus balsamifera (balsam poplar), Fraxinus americana (white ash), Larix laricina (eastern 


larch), Picea mariana (black spruce), and mostly south of the White Mountains, Tsuga 

canadensis (hemlock). Trees vary from approximately 25-80% cover, and may form a 

substantial portion of the woody understory strata, depending on overstory tree cover. 

The shrub layer is typically sparse to moderately well developed and may include Alnus 

incana var. americana (speckled alder), Ilex verticillata (swamp winterberry), Nemopanthus 

mucronatus (mountain holly), Toxicodendron radicans (poison ivy), Viburnum nudum var. 

cassinoides (witherod), Lonicera canadensis (Canada honeysuckle), Spiraea alba var. latifolia 

(eastern meadow-sweet), and Cornus sericea (red osier dogwood). Vaccinium corymbosum 

(highbush blueberry) is absent. 

A broad diversity of herbaceous species has the potential to occur. Characteristic herbs shared 

with more acidic hardwood-conifer swamps include Chelone glabra (turtlehead), violets (Viola 

spp.), Platanthera spp. (rein-orchids), Cornus canadensis (bunchberry), and Coptis groenlandica 

(goldthread). Certain species tend to be absent or in lower abundance and constancy including 

Carex trisperma (three-seeded sedge), Osmunda cinnamomea (cinnamon fern), and Sphagnum 

mosses (although all may be present). Other differential species characteristic of this type and 

indicative of seepage and/or somewhat higher nutrient status include black ash, Geum rivale (water 

avens), Senecio robbinsii (Robbins ragwort), Onoclea sensibilis (sensitive fern), Tiarella cordifolia 

(foamflower), Hydrocotyle americanum (water pennywort), Chrysosplenium americanum (golden 

saxifrage), Circaea alpina (dwarf enchanters nightshade), Impatiens capensis (jewelweed), Carex 

stricta (tussock sedge)(particularly var. strictior), Cinna latifolia (slender wood reed), Carex 

gynandra (northern awl sedge), Glyceria striata (small manna-grass), Glyceria melicaria (mannagrass), 

Solidago flexicaulis (zigzag goldenrod), and Thelypteris palustris (marsh fern). 

Mosses are usually abundant and may form a continuous carpet. Although Sphagnum moss 

can be abundant in more acidic examples, it is often less abundant than in spruce swamps. The 

so-called “Brown mosses” (species primarily of the Amblystegiaceae family) are typically 

present in some abundance along with Mnium spp., and various liverworts. 

Potential rare species include Malaxis unifolia (green adders-mouth)*, Solidago purshii 

(Pursh’s goldenrod)*, Galium kamtschaticum (Kamtshatica bedstraw)*, Listera cordata (heartleaved 

twayblade)*, and Listera convallarioides (lily-leaved twayblade)* on somewhat more 

acidic sites. Sites with more intermediate pHs may have certain calcicoles (calcium-loving 

species), typically found in base-rich seepage swamps (see this community for complete list and 

variant descriptions below), but are more likely to be found in more base-rich conditions. 

This swamp type is similar in many respects to the red maple-black ash/swamp saxifrage 

swamp and the red maple/sensitive fern-tussock sedge swamp types. It differs from these more 

southern swamps by the generally reduced importance of red maple, increased importance of 

more northern or boreal hardwoods, conifers, shrubs, and herbs, and by the absence of Saxifraga 

pensylvanica (swamp saxifrage), Symplocarpus foetidus (skunk cabbage), Lindera benzoin 

(spicebush), and other southern species. Transitional examples do exist where both southern and 

northern species overlap. 


The following variants deserve further study and consideration as distinct communities or as 

significant variants within the broader community concept. 

1. Acidic to sub-neutral basin-seepage swamp variant (S3): Moderately acidic conditions 

prevail here, although the herb flora is not as limited as in red spruce-hardwood swamps 

described from the White Mountains. These examples lack species restricted to basic 

conditions, generally occur in small to large flat or very slightly sloped basins, and may 

exhibit more seasonal water table fluctuation than sloped swamps described below due to 

proximity to stream drainages and larger corresponding drainage areas. This is the 

northern analogue to the red maple/sensitive fern-tussock sedge basin-seepage swamp 

described elsewhere, but not enough examples have been documented to substantiate it as a 

distinct community type (n=7). Some hemlock-Taxus canadensis (Canada yew) swamps 

appear to be fairly distinct and are included here, but are only described from two sites. 

2. Sub-neutral to basic basin-seepage swamp variant (S1): This type is similar to the 

first variant but contains a more significant presence of calcicoles. Conditions 

appropriate for these species may only occur as localized areas within an otherwise more 

extensive and acidic swamp where base-rich groundwater discharge occurs. Many of 

these species are found primarily in association with rich fens or northern white cedar 

swamps, but have the potential to occur in this swamp type as well, particularly in small 

canopy opening areas. These species include Rhamnus alnifolia (alder-leaved 

buckthorn), Cypripedium reginae (showy lady’s slipper)*, Carex castanea (chestnut 

sedge)*, Carex baileyi (Bailey’s sedge)*, Carex bebbii (Bebb’s sedge)*, Cypripedium 

pubescens (large yellow lady’s-slipper)*, and Liparis loeselii (Loesel’s twayblade)*. 

3. Sub-neutral-basic sloped seepage swamp variant (S1S2): This variant includes black 

ash dominated swamps formed on gentle, but definitively sloped terrain, often with 

visible evidence of surface seepage and non-entrenched drainage channels. Soils are 

grayish or gleyed silty loams with or without a shallow muck layer (histic epipedon). 

The shallow organic layer, sloped terrain and dominance of black ash may justify 

designating this type a distinct community type. This variant has a distinctly northern 

distribution north of and including Lancaster (n=6+). 

DISTRIBUTION: Primarily found north of the White Mountains in the Connecticut Lakes, 

Mahoosuc-Rangley Lakes, and Vermont Piedmont subsections, and occasional in the White 

Mountain, Sebago-Ossipee, and probably NH Upland subsections from approximately 800-2000 

ft. elevation. Examples transitional to the related red maple-black ash/swamp saxifrage type 

appear to occur at somewhat lower elevations (ca. 500 ft.). 

COMMENTS: Variation within the type is not well understood presently. Although this is a 

distinct group of swamps in many respects, it is still broadly defined in the sense that significant 

variation is apparent within and between examples included, and the similarities to certain other 

types (e.g., red spruce-hardwood/violet and red maple-black ash/swamp saxifrage types) (n=16). 


GOOD EXAMPLES: Coleman State Park (Stewartstown); Moore Reservoir vicinity (Littleton); part 

of Brown Ash Swamp (Thornton); Umbagog State Park (Errol); South of Cleveland Mtn. 

(Bethlehem). 


• Northern white cedar-balsam fir seepage swamp (G4 S2) 

Thuja occidentalis-Abies/Mitella nuda-Carex pedunculata/Rhytidiadelphus triquetrus saturated 

forest/woodland 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: Swamps dominated by Thuja occidentalis 

(northern white cedar) are moderately acidic to circumneutral peatlands restricted to northern 

New Hampshire. Northern white cedar is a boreal species that approaches its southeastern limit 

in New Hampshire where it occurs only sparingly south of the 44th parallel, and is essentially 

absent from the interior core of the White Mountains. It becomes increasingly abundant as one 

moves north in the state, and is more abundant in adjacent Maine and Vermont. In New 

Hampshire, it is particularly abundant in the Frontenec Formation area (formerly Waits River 

Formation) in the Stewartstown and Colebrook vicinity. 

Although it occurs in nearly pure stands, northern white cedar is often associated with other 

conifers and to some extent northern hardwoods (see the northern hardwood-black ash-conifer 

seepage swamp description for examples with relatively minor amounts of cedar). Nearly closedcanopy 

stands create a deeply shaded understory (sampled stands range from 50-100% cover). In 

mature examples, the typical structure consists of overstory canopy heights of 12-18 m (40-60 ft.) 

with occasional to frequent leaning trees and blowdowns, a moderately well developed tree 

subcanopy, a sparse shrub understory, well developed hummock-hollow topography and dense 

carpet of bryophytes, and a sparse to moderate herb cover. Trees can readily exceed 150 years of 

age (some examples in New Hampshire exceed 240 years; maximum ages for cedar rangewide 

approach 1300 years, although on cliff habitats only). Most swamps range from 1-50 acres, with at 

least two or three examples in New Hampshire nearly 100 acres or more. 

SOILS/GEOLOGY/HYDROLOGY: Soils are moderately deep, well-decomposed (sapric), very poorly 

drained peats, usually over silt soils or occasionally bedrock, sand, or gravel. Peat depths 

average 135 cm (n=30 sites; standard deviation=62) with a range of 20-240 cm (only 4 of 30 

sampled sites were less than 70 cm). Shallower soils are often found toward the swamp margins. 

Seasonal water fluctuations are apparent and result from variation in upland runoff and/or 

seasonal groundwater flow. Most swamps are not directly flooded by regular over-bank flow 

from adjacent streams. Circumneutral to basic groundwater seepage or near-surface flow is 

apparent in many examples, although some sites are best described as weakly acidic. Average 

pH was 6.14 (n=32) with a range of 4.9-7.5 (standard deviation=0.75; highest and lowest values 

of 4.1 and 7.8 not included). Average conductivity is 57 uS (n=29) with a range of 10-140 uS 

(standard deviation=43). When high values of 210, 240, 280, and 330 from 2 sites are included, 

the average was 82 uS. 


CHARACTERISTIC VEGETATION: Over 200 species of vascular plants and over 61 species of 

bryophytes have been documented from northern white cedar swamps in New Hampshire (182 

species documented just within 25 plots). Of the 182 species, 56 (31%) occurred in only one 

plot, while an additional 25 (14%) occurred in 3 or fewer plots; correspondingly, 101 species 

(55%) occurred in 4 or more plots. 

The vegetation description here applies to northern white cedar swamps in general. The 

more or less distinct variants of this general description are described below. Northern white 

cedar is the dominant or co-dominant tree species, with Abies balsamea (balsam fir) almost 

always present and next in abundance. Fraxinus nigra (black ash) is usually present though not 

necessarily abundant. Other frequent to occasional species, usually in lower abundance, include 

Betula alleghaniensis (yellow birch), Acer rubrum (red maple), Picea glauca (white spruce), 

Larix laricina (eastern larch), Picea rubens (red spruce), and Picea mariana (black spruce). 

Tall shrubs are of sparse to moderate density, although sometimes diverse despite low 

abundance; open canopy areas may have a higher density shrub understories. Lonicera 

canadensis (Canada honeysuckle) and Viburnum nudum var. cassinoides (witherod) are the most 

frequent, Nemopanthus mucronatus (mountain holly), Cornus sericea (red osier dogwood), and 

Acer spicatum (mountain maple) are also frequent, Alnus incana var. americana (speckled 

alder) is occasional, and Ilex verticillata (swamp winterberry), Amelanchier bartramiana 

(Bartram’s shadbush), Sorbus americana (mountain ash), and Corylus cornuta (beaked hazelnut) 

are infrequent to rare. Trailing shrubs, dwarfed shrubs, herb-like dwarfed creeping shrubs are 

always present in some abundance; the most frequent of these include Cornus canadensis 

(bunchberry), Gaultheria hispidula (creeping snowberry), Linnaea borealis (twinflower), Ribes 

lacustre (bristly black currant), and Taxus canadensis (Canada yew). Rhamnus alnifolia (alderleaved 

buckthorn) and Vaccinium myrtilloides (velvet-leaved blueberry) are occasional. 

Characteristic herbs that may be good differential species relative to other swamp types 

include Mitella nuda (naked miterwort), Carex pedunculata (long-stalked sedge), Pyrola 

secunda (one-sided pyrola), and although less frequent, Platanthera obtusata (blunt-leaved 

orchis), and Rhamnus alnifolia (alder-leaved buckthorn). Characteristic and frequent herbs (in 

approximately descending order of frequency) include Carex trisperma var. trisperma (threeseeded 

sedge), Osmunda cinnamomea (cinnamon fern), Coptis groenlandica (goldthread), Rubus 

pubescens (dwarf raspberry), Carex pedunculata, Mitella nuda, Oxalis acetosella (wood sorrel), 

Dalibarda repens (Dalibarda), Trientalis borealis (starflower), Carex intumescens (inflated 

sedge), Thelypteris phegopteris (broad beach fern), Carex leptalea (delicate sedge), Dryopteris 

cristata (crested wood-fern), Tiarella cordifolia (foamflower), and Athyrium filix-femina (lady 

fern). Foamflower appears to be a good indicator of somewhat enriched swamps (average pH 

when present=6.5 (n=6 sites), standard deviation=0.44). 

Characteristic bryophytes that are common or fairly frequent in the nearly ubiquitous 

bryophyte groundcover include Hylocomium splendens, Amblystegium riparium, Rhytidiadelphis 

triquetrus, R. subpinnatus, Thuidium delicatulum, Bizzania trilobata, Rhizomnium punctatum, 


Rhizomnium appalachianum, Fissidens adiantoides, Calliergon cordifolium, Sphagnum 

girgensohnii, S. subtile, S. russowii, Plagiochila asplenioides, and Trichocolea tomentella. 

Potential rare species of cedar swamps or fen-like openings within swamps include 

Petasites frigidus var. palmatus (sweet coltsfoot)*, Cypripedium reginae (showy lady’s 

slipper)*, Carex castanea (chestnut sedge)*, Carex baileyi (Bailey’s sedge)*, Carex bebbii 

(Bebb’s sedge)*, Calypso bulbosa (Calypso orchid)*, Cypripedium parviflorum (small yellow 

lady’s-slipper)*, Cypripedium pubescens (large yellow lady’s-slipper)*, Cypripedium arietinum 

(ram’s head lady’s slipper)*, and Liparis loeselii (Loesel’s twayblade)*. All of these species 

prefer nutrient-rich wetlands and were not present in most cedar swamps investigated. 

1. Typic variant (Thuja occidentalis-Abies/Mitella nuda-Carex pedunculata/ 

Rhytidiadelphus triquetrus Saturated Forest/Woodland): This variant is characterized by 

a high non-Sphagnum moss cover and a diverse herb and shrub composition. Boreal 

dwarf, trailing, herb-like shrubs are common. Miterwort, peduncled sedge, one-sided 

pyrola, and black ash are usually present in low abundance, while sheep laurel and black 

spruce are generally absent. Southern, low elevation examples (including lower 

elevations of Mahoosuc-Rangely Lakes subsection) appear to have a higher abundance of 

cinnamon fern, black ash, sensitive fern, and foam flower. Soil pH ranges between 6.1- 

7.35 (8.25 outlier) (n=11), and conductivity ranges between 30-140 uS (with outliers of 

210 and 305) (n=11). Peat/muck depths range from 70-225 cm (n=11). 

This variant is found in very poorly drained, small upland basins near headwater 

positions (especially in the VT Upland subsection), particularly in calcareous regions. A 

few examples also occurred in larger, more diverse swamp settings. It is distributed in 

the VT Upland, Mahoosuc-Rangley Lakes, and CT Lakes subsections at elevations 

between 800-1900 ft. with one example at 500 ft. Good examples are Tinkerville, 

Lyman, Gardner, Monroe, French, Prospect, Littleton, Mile, Ramblewood, Mud Pond 

Brundage, Jacquith, Hurlbert, and Back Pond. 

2. Boreal calcareous variant (Thuja occidentalis/Rhamnus alnifolia Forest/Woodland 

variant): This variant is marginally distinguished from the typic variant by the presence 

of alder-leaved buckthorn and hairy honeysuckle, a higher abundance of Carex leptalea 

(delicate sedge) and Carex disperma (two-seeded sedge), and a low abundance or 

absence of cinnamon fern. This variant needs to be substantiated by descriptions from 

other parts of the region. Soil pH is presumably greater than 6 (7.8, n=1), and 

conductivity is presumably higher than average (185-240, n=2). Peat/muck depths range 

between 130-185 cm (n=3). 

In New Hampshire, this variant was only found in Hurlbert Swamp, a very poorly 

drained large boreal wetland complex influenced by calcareous bedrock in the CT Lakes 

subsection at ca. 1500 ft. 

DISTRIBUTION: North of the 44th parallel, excluding the interior White Mountains (VT 

Piedmont, Mahoosuc-Rangley, and Connecticut Lakes subsections) with disjunct occurrences in 


the Conway-Madison area (White Mountain and Sebago-Ossipee subsections). Elevations range 

from 500-1920 ft. 

COMMENTS: Cross-state comparisons should distinguish whether variation found within the state 

is local or whether it applies to a broader regional context. 

GOOD EXAMPLES: Hurlbert Swamp (Colebrook); Whaleback Pond (Errol); disjunct occurrence at 

White Horse cedar swamp (Albany). 

SOURCES: Sperduto and Engstrom (1998). Moss determinations by Natalie Cleavitt for NH 

Heritage. 

• Boreal acidic northern white cedar swamp (G4 S1) 

Thuja occidentalis/Kalmia angustifolia/Sphagnum forest/woodland 

CHARACTERISTIC VEGETATION: Sphagnum moss is abundant, and there is a well developed 

shrub layer compared to northern white cedar-balsam fir seepage swamps. The average cover 

and diversity in the herb layer is somewhat lower, while there is a greater abundance/frequency 

of black spruce, sheep laurel, creeping snowberry, mountain holly, and sometimes alder. 

SOILS/GEOLOGY/HYDROLOGY: The pH less than 6 (4.1-5.9) the conductivity ranges between 30- 

50 uS (n=3). Peat/muck depths range from 125-230 cm (n=3). This natural community is 

associated with large, acidic, northern, very poorly drained basins, often with spruce-fir swamps. 

DISTRIBUTION: Known from the Mahoosuc-Rangley Lakes and CT Lakes subsections (ca. 1200- 

1300 ft.). 

GOOD EXAMPLES: Whaleback, Umbagog, Chickwolnepy. 

SOURCES: Sperduto and Engstrom (1998). Moss determinations by Natalie Cleavitt for NH Heritage. 

• Seasonally saturated northern white cedar seepage forest (S2) 

Thuja occidentalis/Solidago flexicaulis seasonally saturated forest 

CHARACTERISTIC VEGETATION: This community is distinguished by a low moss cover on slightly 

to moderately sloped ground with a sparse shrub layer and a greater abundance of upland herbs 

including zigzag goldenrod, blue-bead lily, Carex arctata (drooping wood sedge), Indian 

cucumber, shining clubmoss, foamflower, sugar maple, and Jack-in-the-pulpit. New Hampshire 

examples were not targeted in plot sampling in this study. It is considered a fairly distinct 

variant of the typic type or a marginally distinct community type. 

SOILS/GEOLOGY/HYDROLOGY: Shallow, well decomposed muck (generally

DISTRIBUTION: Known from the VT Upland, Mahoosuc-Rangley Lakes and CT Lakes 

subsections. 

GOOD EXAMPLES: Lime Pond, Patrick Woodlot, the example at Coolidge Brook is transitional to 

swamp types. 


Heritage. 

• Northern white cedar-hemlock-red maple swamp (G4 S2) 

Thuja occidentalis-Tsuga canadensis-Acer rubrum Forest 

CHARACTERISTIC VEGETATION: These diverse swamps have hemlock, “seepage” plants, and 

several plants absent or sparse in more northern swamps (notably hemlock, partridgeberry, 

canopy red maple and white ash, trailing arbutus, and witch hazel). It shares some similarities to 

seepage swamp types south of the White Mountains. 

SOILS/GEOLOGY/HYDROLOGY: Conductivity and pH were not sampled. Muck was only 20 cm 

deep in the one soil profile described. It is found in moderately small basins in headwater 

seepage areas, with saturated to seasonally saturated (poorly to very poorly drained) soils. 

DISTRIBUTION: Known from the Conway-Madison area (Sebago-Ossipee subsection at transition 

to White Mountain subsection) 


Heritage. 

WEAKLY ACIDIC TO ACIDIC SWAMP FORESTS/WOODLANDS 

• Red maple/sensitive fern-tussock sedge basin/seepage swamp (S2S3) 

Acer rubrum/Onoclea sensibilis-Carex stricta basin/seepage swamp 

This swamp is a type of acidic seepage swamp characterized by a diverse assemblage of 

herbaceous species, relatively little Sphagnum moss, and saturated or seasonally saturated to 

seasonally flooded soils. The swamps may be small or very large (10-100 acres) and typically 

occupy headwater basins that give rise to drainages or are found along drainages where seepage, 

non-channeled upland runoff, and precipitation all contribute to the water budget. Seepage may 

only be sub-surface and not physically evident (e.g., small streams and springs may or may not 

be evident, or only close to outflow areas or on slightly sloped margins of the basin). Generally, 

there is no pronounced seasonal flooding from overbank flow of a nearby stream, but subsurface 

through-flow from uplands or other parts of the basin may be more substantial than in stagnant 

basin swamps. Subsurface groundwater discharge is likely in at least some of these swamps. 

These swamps are often found with other swamp communities in a larger mosaic. 

The tree layer may form a forest (>60%) canopy or a more commonly a woodland cover (25- 

60%), and consists of Acer rubrum (red maple), with lesser quantities of Ulmus americana 


(American elm) and other hardwoods, and no or few conifers. A diverse shrub layer is typical, 

including abundant Ilex verticillata (swamp winterberry); Vaccinium corymbosum (highbush 

blueberry) is usually present but less abundant than in basin swamps, and Viburnum dentatum 

var. lucidum (arrow-wood), Alnus rugosa (speckled alder) and Spiraea latifolia (meadow-sweet) 

are occasional. Rhus vernix (poison sumac), Toxicodendron radicans (poison ivy), Sambucus 

canadensis (elderberry), Lindera benzoin (spicebush), Viburnum lentago (nannyberry), and 

Cornus amomum (silky dogwood) may be present but typically in low abundance (generally 

absent from acidic basin swamps). Carex stricta (tussock sedge) and Onoclea sensibilis 

(sensitive fern) are usually abundant or co-dominant herbs, but not consistently dominant in all 

examples. Impatiens capensis (jewelweed) is frequent. Other frequent or occasional wetland 

herbaceous species include Iris versicolor (blue flag), Lysimachia terrestris (swamp candles), 

Carex crinita (drooping sedge), Osmunda regalis (royal fern), and Calamagrostis canadensis 

(blue-joint). Osmunda cinnamomea (cinnamon fern) may be present but is not dominant 

throughout. Carex bromoides (broom sedge) is abundant in some examples. Mosses may be 

abundant or diverse, but Sphagnum moss is absent or typically comprises less than 5% cover. 

Hummock-hollow topography may be absent to moderately well developed. Upland species 

found on large hummocks of acidic basin swamps appear to be less abundant in these swamps 

(e.g., Aralia nudicaulis (wild sarsaparilla), Mitchella repens (partridge berry), Quercus rubra 

(red oak), etc.). 

• Red spruce/cinnamon fern-three seeded sedge/Sphagnum swamp (S3) 

Picea rubens/Osmunda cinnamomea-Carex trisperma/Sphagnum saturated woodland swamp 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This spruce swamp community is dominated 

by Picea rubens (red spruce)(25-50+% cover) with a shallow to moderate depth peat layer. 

Carpets of Sphagnum moss, Carex trisperma var. trisperma (three-seeded sedge), and Osmunda 

cinnamomea (cinnamon fern) form a lush understory with a light to moderate tall shrub layer, 

sparse dwarf heath shrub layer, and low to moderately developed hummock-hollow topography. 

The prominence of red spruce rather than Picea mariana (black spruce) and a poorly developed 

dwarf shrub heath layer is indicative of slightly more minerotrophic conditions and less 

permanently saturated conditions than found in most black spruce woodlands. These swamps are 

found isolated from or as a part of larger wetland complexes in valley flats, margins of small 

stagnant drainages, other swamp or lake basins, and on benches of mountain or hill slopes. Little 

direct streambank overflow or surface drainage is evident, except in the red sprucehardwood/violet 

variant described below. These swamps appear to be more abundant in the 

White Mountain region than black spruce-larch swamps due to the prevalence of topogenicallyinfluenced 

basins in mountainous terrain, the corresponding lack of larger, stagnant basins with 

little upland runoff, and perhaps to some extent, the abundant seed availability of red spruce 

from surrounding upland habitats. 

SOILS/GEOLOGY/HYDROLOGY: Soils are acidic, nutrient poor (oligotrophic), very poorly drained 

mineral histic and histic epipedons with organic peat horizons usually 10-40 cm deep. A 


saturated to seasonally saturated water regime is probably typical. Underlying mineral soils 

range from coarse sand and gravel to finer sand or silts, often derived from ice-contact deposits 

along drainages, glacial slackwater deposits in broader valley basins, or till sediments. The 

shallower peat soils and more rapid decomposition rates of these swamps (compared to black 

spruce swamps) indicate slightly greater nutrient status. This probably results from a 

combination of more broadly fluctuating water levels and a greater influence of minerotrophic 

water from surrounding uplands and/or horizontal groundwater movement through these 

swamps. 

CHARACTERISTIC VEGETATION: Red spruce is typically the most abundant tree species, with 

lesser amounts of Abies balsamea (balsam fir), and occasionally some black spruce, red maple, 

and birches. Canopies generally do not exceed 50% cover in sampled stands, although dense 

regeneration stands with greater canopy closure may be found. The tall shrub layer is sparse to 

moderately abundant, depending to some extent on degree of canopy closure. Nemopanthus 

mucronatus (mountain holly) is common, with occasional Viburnum nudum var. cassinoides 

(witherod), Ilex verticillata (swamp winterberry), and Alnus incana var. americana (speckled 

alder). Speckled alder may be quite abundant in examples near stream margins or areas 

influenced by upland runoff (see variants below). Vaccinium corymbosum (highbush blueberry) 

is absent from northern examples, although may be present in disjunct examples in central and 

southern New Hampshire. Dwarf heath shrubs are absent or in low abundance, although Kalmia 

angustifolia (sheep laurel) and Gaultheria hispidula (creeping snowberry) are occasional. 

Herbaceous species are moderately abundant with Carex trisperma var. trisperma (threeseeded 

sedge) (ca. 5-90% cover) and cinnamon fern (

fern and three-seeded sedge are usually present, but often in lower abundance. Species 

richness appears to be slightly greater than the typic variant (23-26 species/400 m 2 ; n=4 

sites), perhaps indicative of slightly elevated nutrient status or greater light availability 

compared to the typic variant. Differential species include Viola macloskeyi (wild white 

violet) and other violets, Chelone glabra (turtlehead), Platanthera clavellata (green wood 

orchis), P. dilatata (white bog orchis) and other rein-orchids, and Veratrum viride 

(hellebore), among other herbs. Sphagnum is usually abundant or dominant in the moss 

layer. Peat depth is generally shallow, although some examples appear to have depths 

exceeding one meter. This variant is similar to northern hardwood-conifer-black ash 

swamps, but generally lacks Fraxinus nigra (black ash) and numerous other species 

indicative of more minerotrophic conditions. 

Potential rare species include Malaxis unifolia (green adders-mouth)*, Galium 

kamtschaticum (Kamtshatica bedstraw)*, Listera cordata (heart-leaved twayblade)*, and Listera 

convallarioides (lily-leaved twayblade)*. 

DISTRIBUTION: Primarily documented from the White Mountain and Sebago-Ossipee 

subsections, but probably occurs in the Mahoosuc-Rangley Lakes, Connecticut Lakes, Vermont 

Piedmont, and NH Upland subsections. Elevations of known examples range from ca. 700 ft. to 

over 2000 ft. This community may range to higher elevations, although black spruce becomes 

increasingly more prominent here. 

COMMENTS: Similar to the black spruce-larch swamps but generally without a well developed 

dwarf heath layer. 

GOOD EXAMPLES: Typic variant: Elbow Pond (Woodstock); parts of Trudeau Road vicinity 

(Bethlehem); parts of Spruce Brook (Berlin); Big River vicinity (Barnstead). Red sprucehardwood/violet 

variant: Petty Brook vicinity (Langdon); Rickers Knoll and Langdon Brook 

vicinity (Chatham); Zealand River vicinity (Bethlehem); part of Brown Ash Swamp (Thornton) 

(n=10 sites). 


FOREST SEEPS 

Forest seeps form where groundwater is discharged at or near the soil surface, either 

continuously or for substantial portions of the year. They are found in headwater positions of 

streams, along “seepage runs” of small drainages, on benches and sloping terrain of upland till 

hillsides, along upland margins of swamps, and on steep faces of river terraces. Groundwater 

usually emerges where the surface of an impervious or slowly pervious soil layer (hardpan, silt, 

or clay material) forces water to the surface, or other situations where the ground surface 

intercepts the water table on sloped terrain. Most seeps occur on slopes ranging from 1-25 or 

more degrees and have mineral soil or a shallow muck horizon at the surface (less than 15-30 cm 

deep) and weakly acidic (subneutral) to circumneutral pHs. Organic matter does not accumulate 

substantially presumably because of the continuous supply of more or less minerotrophic water 


and the well-oxygenated soils maintain a relatively rapid decomposition rate compared to more 

stagnant, flat wetlands that tend to accumulate more organic matter (e.g., swamps and bogs). 

The mineral level of seepage water is probably strongly influenced by the nature of surface 

material (soil and underlying bedrock) through which it flows. Seeps are divided here into three 

broad types: acidic, subneutral, and circumneutral types. Calcareous forest seeps have not been 

described from New Hampshire; the closest equivalent would be calcareous fens in New 

Hampshire which differ by being generally larger than forest seeps, but have a more well 

developed peat layer and many peatland plants indicative of basic pHs. 

In many ways seeps are miniature swamps or marshes, but they differ from their larger 

counterparts in several important respects. They occur as small inclusions within upland forests 

and are therefore considerably shaded. Most are no larger than one to several tree canopies in 

breadth (less than 0.1 acres). They are often isolated from larger wetlands, have mineral soils 

with or without a shallow muck layer (usually not peat), and are usually more permanently 

saturated with a localized and pronounced seepage area compared to larger swamps. 

Functionally, seeps serve as refugia for wetland plants, amphibians (e.g., northern dusky and 

two-lined salamanders, various frogs), and other organisms in upland dominated landscapes, and 

contribute oxygenated water to streams and wetlands. Perennial seepage tends to keep seeps 

cool in the summer, and sometimes snow-free in the winter if seepage is active enough. As 

groundwater is less influenced by seasonal air temperature than are surface water and 

precipitation sources, many seeps probably have relatively stable temperatures. Some seeps may 

only have seasonally active seepage. Despite their small size and scattered distribution, there are 

probably thousands of seeps in the state. Their local and collective significance is greater than 

implied by the area they cover, and as such, seeps warrant protection wherever they occur as 

sensitive wetland “hot-spots” within upland forest dominated landscapes. 

Floristically, many of the wetland plants found in seeps may also be found in seepage 

swamps, although seeps tend to have a higher concentration or abundance of plants diagnostic of 

pronounced seepage. Within larger swamps, focused points of discharge and corresponding 

diagnostic species are usually confined to very small areas or are obscured as subsurface flow on 

a flatter swamp surface. In addition, because of their small size, seeps tend to be more variable 

in composition from one example to the next. Collectively, seeps are quite diverse. In a study of 

17 seeps from around the state (3 different types), 138 species were catalogued, with an average 

of 17 species per seep (NH Heritage data, 1998). About half of these species are found at only 

one seep, and more than two-thirds are found in only two or fewer seeps. Even within a single 

type of seep, 42% of the species are found in only one seep, and 62% in two or fewer seeps. In 

part, seep composition may be so variable because local seed sources, dispersal events, and 

reproductive success of plants is also locally variable. Despite the low incidence of more than ½ 

the species found in seeps, many have narrow ecological requirements and tell us something 

about the conditions at a seep. For instance, while no seep will contain most of the species 

diagnostic of pronounced seepage conditions, any one seep is likely to have at least a few of 

them. This is probably because of the low probability that seeds of a particular seep plant 

actually gets distributed to such small “target areas,” and the difficulty of establishing and 


maintaining a population in such a small area under competition with other plants once they 

arrive. Although this contributes a more random element to plant composition of seeps than 

perhaps many larger wetlands, some broad patterns and groups of plants can be distinguished. 

These patterns roughly parallel the patterns seen in larger seepage swamps, although much more 

work is needed to adequately describe seep variation in the state. 

Species usually diagnostic of pronounced seepage include Chrysosplenium americanum 

(golden saxifrage), Carex scabrata (rough sedge), Hydrocotyle americanum (water pennywort), 

Circaea alpina (dwarf enchanters nightshade), Glyceria melicaria (manna-grass), Impatiens 

capensis (jewelweed), Platanthera dilatata (white bog orchis), Cardamine pensylvanica 

(Pennsylvania bittercress), Rubus pubescens (dwarf raspberry), Galium kamtschaticum 

(Kamtshatica bedstraw)*, Listera convallarioides (lily-leaved twayblade)*, Scirpus microcarpus 

(barberpole bulrush), Mnium spp. (a moss), and certain Sphagnum species, such as Sphagnum 

squarrosum. The bryophyte flora of seeps appears to be quite diverse, although there has been 

little specific research done. The cold micro-climate produced by seeps can provide disjunct 

refugia for typically more northern species. For example, Viburnum alnifolium (hobblebush) is 

abundant in the White Mountains, but restricted to seeps and other cool micro-habitats in 

Rockingham County. 

• Acidic Sphagnum seep (S3S4) 

Sphagnum russowii - S. girgensohnii seep 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This community is probably most frequent in 

spruce-fir forests at higher elevations in the White Mountains, but may occur at a broad range of 

elevations in nutrient poor, coniferous settings. It is found on benches, along headwater 

drainages and springs, and on seepy, ledgey slopes. This seep type differs from the Sphagnum 

variant of the subneutral foamflower-graminoid seep by the absence of Tiarella cordifolia 

(foamflower), Carex scabrata (rough sedge), and Glyceria melicaria (manna-grass) that are 

indicative of slightly more minerotrophic conditions. They are equivalent in some respects to 

miniature spruce-fir swamps, and transitional to acidic fen communities in more open examples. 

SOILS/GEOLOGY/HYDROLOGY: Acidic groundwater is implied by the lack of species diagnostic of 

enriched conditions, although few pH measurements have been taken (pHs probably do not 

exceed ca. 5.5). Shallow peat or muck layers (less than 30 cm) are typical over seepy bedrock or 

in headwater positions over sandy loams, particularly in spruce-fir or other nutrient-poor 

coniferous settings. 

CHARACTERISTIC VEGETATION: Trees that may form a dense tall shrub or subcanopy layer 

include Picea rubens (red spruce) or Picea mariana (black spruce) and Abies balsamea (balsam 

fir). The shrub layer is otherwise scant and herbs form a sparse to moderate cover over a dense 

Sphagnum layer. Common Sphagnum mosses include S. girgensohnii, S. russowii, S. centrale, S. 

fallax, and S. squarrosum. Characteristic herbs include Veratrum viride (hellebore), Aster 

acuminatus (whorled aster), Oxalis acetosella (wood sorrel), Thelypteris noveboracensis (New 


York fern), Carex disperma (two-seeded sedge), Carex leptalea (delicate sedge), Carex 

intumescens (inflated sedge), Thalictrum pubescens (tall meadow rue), Osmunda cinnamomea 

(cinnamon fern), Coptis groenlandica (goldthread), Gaultheria hispidula (creeping snowberry), 

Equisetum arvense (field-horsetail), and Aster radula (rough-leaved aster). Galium 

kamtschaticum (Kamtshatica bedstraw)*, Listera cordata (heart-leaved twayblade)* and Listera 

convallarioides (lily-leaved twayblade)* are rare species that may occur in this community. In 

examples transitional to acidic fens, the rare Calamagrostis pickeringii (Pickering’s reed-grass)* 

might be expected. Heath shrubs and fen sedges may be present in some examples, but do not 

reach nearly the prominence found in acidic fens (n=6+ sites). 

DISTRIBUTION: This community occurs in the mountains and low elevation coniferous forest or 

other nutrient poor settings. It is most common above 2500 ft. elevation. 

COMMENTS: This community is similar to spruce-fir swamps but is characterized by active 

seepage that limits peat accumulation and contain more plants restricted to seepage conditions. 

It is also transitional to acidic fen communities, but are typically smaller in size, and lack the 

abundance of fen sedges, heath shrubs, and deeper peat soils of fens. 

GOOD EXAMPLES: Nancy Brook RNA (Livermore); Stony Brook headwaters, Imp Mt. (Beans 

Purchase); above Crystal Cascade (Pinkhams Grant). 

SOURCES: Royte et al. (1996); NH Heritage field surveys. 

• Subneutral forest seep (S3S4) 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This is a broadly defined group of seeps with 

subneutral (weakly acidic) conditions. Four fairly distinct variants are described based on 

differences in dominant life forms and species composition. All have species indicative of 

subneutral conditions that are intermediate between the nutrient poor conditions of acidic seeps and 

the enriched conditions of circumneutral seeps. Although these four variants are reasonably distinct, 

they likely do not represent the full breadth of floristic variation of subneutral seeps in the state. For 

instance, seepage runs along stream headwaters with Caltha palustris (marsh marigold) have not 

been well described, and may be different enough from other seep variants to be described as such. 

The key features of these four variants are given here: 

1. Foamflower-graminoid variant: These seeps are typical of mid-elevation northern 

hardwood and semi-rich mesic forests in the White Mountain region, and probably other 

parts of the state. They are densely herb-dominated with a high graminoid (grass and 

sedge) component and a low to moderate moss cover. Tiarella cordifolia (foamflower), 

Carex scabrata (rough sedge), Glyceria melicaria (manna-grass), and Cinna latifolia 

(slender wood reed) are diagnostic of this variant (three of these four species are present 

in most examples documented). 


2. Subneutral Sphagnum variant: Subneutral Sphagnum seeps are similar to the first type 

and also frequent in the mountains, but have a moderate to dense layer of Sphagnum 

moss, and typically more sparse herb layer. 

3. Bryophyte-violet variant: These seeps are dominated by non-Sphagnum mosses and 

liverworts. The herb layer is variable; some examples have a dense herb layer over the 

bryophyte layer while others are dominated solely by bryophytes. Violets are abundant 

in two examples documented. 

4. Herbaceous-fern glade variant: Herbaceous fern glade seeps are those with a robust 

herb layer including a prominence of ferns and fern allies (horsetails), and other herbs 

such as Impatiens capensis (jewelweed). Graminoids are present but usually not a 

dominant life form as in foamflower-graminoid seeps. 

SOILS/GEOLOGY/HYDROLOGY: Foamflower-graminoid and subneutral Sphagnum seeps have a 

shallow muck layer (typically 10-30 cm) over sand or silt loams on slopes ranging from 1 to 24 

degrees. Most are headwater seeps associated with ephemeral or permanent streams. pH’s are 

subneutral and probably range from ca. mid-5s to mid 6s (one seep sampled had pHs ranging 

from 5.3-5.8). Nutrient levels are probably moderate to moderately high (mesotrophic) as 

indicated by the plant composition. Bryophyte-violet seeps also have subneutral pHs, tending 

toward circumneutral at one site (6.2-6.6 at Allard Brook in Albany), and have shallow sandy 

muck over sand and gravel soils. They occur on till soils and along terrace slope faces. One 

example of a herbaceous-fern glade seep had 20-25 cm of muck over fine sand along a steep 

river terrace slope. 

CHARACTERISTIC VEGETATION: 

1. Foamflower-graminoid variant (Tiarella cordifolia-Carex scabrata-Glyceria 

melicaria-Cinna latifolia): Herbs include Tiarella cordifolia (foamflower), which is 

usually present and abundant, and either or both Carex scabrata (rough sedge) and 

Glyceria melicaria (manna-grass), which are typically among the dominant species. 

Cinna latifolia (slender wood reed) is also usually present, though usually not dominant. 

Total graminoid cover usually exceeds 35%, fern cover typically ranges from 5-20%, and 

total herbaceous cover exceeds 75% (sometimes >100% due to dense, overlapping 

herbs). Most examples are less than 1/10th acre and have 13-18 herb species present 

(some larger examples have more species). Other characteristic but less constant seep 

species include Rubus pubescens (dwarf raspberry), Impatiens capensis (jewelweed), 

Circaea alpina (dwarf enchanters nightshade), Aster puniceus (purple stemmed aster), 

Chrysosplenium americanum (golden saxifrage), Carex intumescens (inflated sedge), 

Carex gynandra (drooping sedge), Platanthera dilatata (white bog orchid), Rubus spp. 

(blackberries), Geum rivale and other Geum spp. (avens), and Galium spp. (bedstraws) 

(including G. tinctorium and triflorum). Galium kamtschaticum (Kamtshatica bedstraw)* 

is an uncommon to rare species present in some mountain examples. Viola spp. (violets) 

were not present regularly in these seeps. Other frequent plants (with broader habitat 


anges) include Aster acuminatus (whorled aster), Oxalis acetosella (wood sorrel), and 

several ferns including Athyrium filix-femina (lady fern), Dryopteris campyloptera 

(mountain wood fern), Dryopteris intermedia (intermediate wood fern), Thelypteris 

phegopteris (broad beach fern), Onoclea sensibilis (sensitive fern), and Osmunda 

cinnamomea (cinnamon fern). Several other plants diagnostic of seeps may occur but are 

less frequent, including Cardamine pensylvanica (Pennsylvania bittercress), Chelone 

glabra (turtlehead), Carex disperma (two-seeded sedge), Hydrocotyle americanum (water 

pennywort), Carex leptalea (delicate sedge), Epilobium coloratum (purple-leaved 

willow-herb), Veratrum viride (hellebore), and Equisetum sylvaticum (wood horsetail). 

Non-Sphagnum mosses contribute a sparse to moderate cover (less than 25%) and 

Sphagnum mosses are generally sparse. Species composition of mosses is poorly 

documented. Trees largely reflect the surrounding forest type (northern hardwoods and 

spruce-fir); within the seeps Betula alleghaniensis (yellow birch) is common, while Abies 

balsamea (balsam fir), Picea rubens (red spruce), and Acer pensylvanicum (striped 

maple) are occasional. Shrubs frequently include Acer spicatum (mountain maple) and 

Viburnum alnifolium (hobblebush) (n=9). 

2. Subneutral Sphagnum variant: This variant differs from the subneutral foamflowergraminoid 

seeps by the presence of a moderate to dense carpet of Sphagnum moss and 

less dense herb layer; it differs from acidic Sphagnum seeps by the presence of species 

indicative of more minerotrophic conditions including Tiarella cordifolia (foamflower), 

Carex scabrata (rough sedge), Glyceria melicaria (manna-grass), Gymnocarpium 

dryopteris (oak fern), Mitella diphylla (two-leaved miterwort), and Onoclea sensibilis 

(sensitive fern), among other species. Sphagnum squarrosum appears to be frequent, 

while S. girgensohnii and S. fallax are also probably common in this community. 

Dryopteris spp. (wood ferns), Huperzia lucidula (shining clubmoss), Aster acuminatus 

(whorled aster), Oxalis acetosella (wood sorrel), and other northern hardwood forest 

herbs may be present. Trees and shrubs typically include Alnus incana var. americana 

(speckled alder), Picea rubens (red spruce), Betula alleghaniensis (yellow birch), and 

Abies balsamea (balsam fir). Galium kamtschaticum (Kamtshatica bedstraw)*, Listera 

cordata (heart-leaved twayblade)*, and Listera convallarioides (lily-leaved twayblade)* 

are rare species that may occur in this community (n=5). 

3. Bryophyte-violet variant (Viola spp./Bryophyte): Bryophytes (mosses and liverworts) 

dominate with an apparent paucity of Sphagnum, and sometimes to the exclusion of 

herbs. These seeps may be associated with a strong coniferous overstory component 

(e.g., >50%). The primary diagnostic plants of Foamflower-Graminoid seeps (Tiarella 

cordifolia (foamflower), Carex scabrata (rough sedge), Glyceria melicaria (mannagrass), 

and Cinna latifolia (slender wood reed)) are sparse or absent. Seepage plants may 

include Viola spp. (violets)(including Viola cucullata), Chrysosplenium americanum 

(golden saxifrage), Carex gynandra (drooping sedge), Circaea alpina (dwarf enchanters 


nightshade), and Rubus pubescens (dwarf raspberry), among others. Arisaema triphyllum 

(Jack-in-the-pulpit) and Onoclea sensibilis (sensitive fern) may also be present (n=2). 

4. Herbaceous-fern glade variant (Osmunda-Onoclea-Equisetum-Impatiens): Dense herb 

layers with prominent fern and horsetail components are typical of this variant. The moss 

layer is variable. Herbs include Onoclea sensibilis (sensitive fern), Osmunda 

cinnamomea (cinnamon fern), Athyrium filix-femina (lady fern), Osmunda claytoniana 

(interrupted fern), Equisetum sylvaticum (wood horsetail), Impatiens capensis 

(jewelweed), and Carex stipata (awl sedge), among other seep plants. 

DISTRIBUTION: Foamflower-graminoid and subneutral Sphagnum variants: Documented 

examples occur from 1300-3100 ft. elevation in the northern hardwood and northern hardwoodspruce-fir 

zone north of and including the White Mountains. They probably also occur further 

south in the Sebago-Ossipee and NH Uplands subsections in appropriate forest settings. 

Bryophyte-violet seeps are documented from the White Mountain region (700-1700 ft. 

elevation), but are probably of wider distribution (e.g., NH Uplands and Sebago-Ossipee region). 

Herbaceous-fern glade seeps are documented from the Coastal Plain subsection (ca. 700 ft.), but 

are probably of broader distribution. 

COMMENTS: Other herb-dominated subneutral seeps may exist in New Hampshire but are 

presently not described. The first three variants are described almost exclusively from the White 

Mountain region, and are collectively more common than circumneutral seeps. Bryophyte 

dominated seeps are fairly distinct but poorly documented. Much more research is needed on 

this broad type, particularly on the bryophyte composition. 

GOOD EXAMPLES: Foamflower-graminoid variant: Jeffers Mtn. & Black Mtn. (Benton); Kelsey 

Mt. (Millsfield); Spruce Brook (Berlin); Falling Waters trail (Lincoln); Lincoln Brook (Lincoln). 

Sphagnum variant: Elbow Pond (Woodstock); Trudeau Rd. vicinity (Bethlehem); Moriah Brook 

headwaters (Beans Purchase); Fairy Spring, Ice Gulch (Randolph); Ammonoosuc Lake 

(Bethlehem). Bryophyte-violet variant: Allard Brook (Albany); Shingle Pond vicinity 

(Chatham). Herbaceous-fern glade variant: Merrimack River terrace slope (Sanbornton). 


• Circumneutral hardwood forest seep (S3) 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: Circumneutral forest seeps are those with pHs 

near neutral (ca. 6.5-7.4) and a higher nutrient availability than subneutral or acidic seeps (below 

ca. 6.4 and 5.3, respectively), as indicated by plants. They are essentially small, wet or “supermesic” 

enriched hardwood forests and occur as small orbicular seeps or as linear “seepage runs” 

within a forest, or zones along river terrace slopes. A mixture of classic seepage and other 

wetland plants along with rich mesic hardwood plants is characteristic. They are treated here as 

one broadly defined group with 3 tentative variants described; future research should seek to 

substantiate and refine these descriptions as needed. 


SOILS/GEOLOGY/HYDROLOGY: Soils are either shallow mucks or silty, gravelly mucks (10-25 

cm) over silt loams or silt or clay mineral soils at the surface, derived from circumneutral 

bedrock, till, or marine silt and clay sediments. pHs probably exceed 6.5 in most examples (7.4 

at one documented example). pHs higher than 7.4 may indicate a presently undocumented 

calcareous seep. 

CHARACTERISTIC VEGETATION: The presence of rich-site plants along with other seepage plants 

differentiates this type from subneutral seeps. Diagnostic rich-site plants include the trees Acer 

saccharum (sugar maple), Fraxinus americana (white ash), Fraxinus nigra (black ash), and Tilia 

americana (basswood), and herbs and shrubs including Laportea canadensis (wood nettle), 

Matteuccia struthiopteris (ostrich fern), Solidago flexicaulis (zigzag goldenrod), Carex 

plantaginea (plantain-leaved sedge), Caulophyllum thalictroides (blue cohosh),Diplazium 

pycnocarpon (narrow-leaved spleenwort), Polystichum acrostichoides (Christmas fern), 

Dryopteris goldiana (Goldie’s fern)*, Actaea alba (white baneberry), Cypripedium pubescens 

(large yellow lady's-slipper)*, Botrychium virginianum (rattlesnake fern), Adiantum pedatum 

(maidenhair fern), Rubus odoratus (purple flowering raspberry), and Viola pubescens (downy 

yellow violet). Other documented species include Viola spp. (violets), Athyrium filix-femina 

(lady fern), Gymnocarpium dryopteris (oak fern), Thalictrum pubescens (tall meadow rue), 

Thelypteris palustris (marsh fern), Glyceria striata (small manna-grass), and Galium spp. 

(bedstraws). Equisetum scirpoides (dwarf scouring-rush) is an uncommon plant that may be 

expected in northern seeps in coniferous or some deciduous forests. 

1. Typic northern hardwood variant: As described above, one recognizable expression of 

circumneutral hardwood seeps are seepy fern and nettle glades that have a high cover 

contributed by ferns, particularly lady fern and/or ostrich fern, and wood nettle. Other 

expressions may contain species also found in calcareous fens such as large yellow lady’s 

slippers*, Cystopteris bulbifera (bulblet fern), Liparis loeselii (Loesel’s twayblade)*, and 

Carex bebbii (Bebb’s sedge)*, particularly in more northern calcareous regions. Carex 

gynandra (drooping sedge) is much more likely in northern seeps than in coastal seeps, 

where it is replaced by its similar counterpart Carex crinita (drooping sedge) (n=4). 

2. Coastal/Appalachian variant: Examples in coastal and southern New Hampshire 

contain many of the rich site species listed above in addition to several species apparently 

absent from the typic northern hardwood examples. These include Carex cristatella 

(small-crested sedge)*, Carex crinita (drooping sedge), Lindera benzoin (spicebush), 

Carex radiata (stellate sedge), Carex rosea (rosy sedge), Amphicarpaea bracteata (hog 

peanut), Acer nigrum (black maple)*, Carpinus caroliniana (musclewood), and Betula 

lenta (black birch). Appalachian oaks and hickories are often prominent in the 

surrounding forest. Boreal conifers are absent and red maple was more abundant in 

documented examples. Some examples are almost fen-like with a strong graminoid 

component, including the sedges listed here (n=3). 

3. River terrace slope variant: Seeps along enriched river terrace slopes often contain 

Equisetum hyemale (scouring Rush) and Matteuccia struthiopteris (ostrich fern) along 


with other seep or wetland plants such as Carex scabrata (rough sedge), Impatiens 

capensis (jewelweed), Chelone glabra (turtlehead), and Alnus incana var. americana 

(speckled alder) (n=4). 

DISTRIBUTION: 

1. Typic northern hardwood variant: Subsections north of and including the White 

Mountains (Connecticut Lakes, Mahoosuc-Rangley Lakes, White Mountain, Vermont 

Piedmont), NH Upland and Sebago-Ossipee subsections, probably mostly between 1000- 

2500 ft. elevation. 

2. Coastal/Appalachian variant: Coastal Lowland and probably the Coastal Plain and 

Northern Connecticut River subsections. Known example are ca. 100 ft. elevation or 

less, although the type may be expected up to ca. 1000 ft. elevation. 

3. River terrace slope variant: Known from the Coastal Plain, Northern Connecticut 

River, and Vermont Piedmont subsections (all

(lesser bur reed), Carex intumescens (inflated sedge), Bidens spp. (beggar ticks), Cicuta bulbifera 

(bulblet water hemlock), Calamagrostis canadensis (blue-joint) and Rhamnus frangula (European 

buckthorn). Each of these species occurred in at least 20-50% of the plots. Fifty other species are 

almost entirely restricted to this type but occur less frequently; 32 of these occur in at least two 

plots. Herbaceous cover can be quite high. The largely hummock-restricted upland species Aralia 

nudicaulis (wild sarsaparilla) and Trientalis borealis (starflower) are generally less constant than 

in the other types described, and boreal indicators are absent. Species much less frequent than in 

other types include Tsuga canadensis (hemlock), Nemopanthus mucronatus (mountain holly), 

Carex trisperma (three-seeded sedge) and Kalmia angustifolia (sheep laurel). 

As with other Atlantic white cedar swamp types Vaccinium corymbosum (highbush 

blueberry), Ilex verticillata (swamp winterberry), Osmunda cinnamomea (cinnamon fern), 

Clethra alnifolia (sweet pepperbush), and Sphagnum spp. (Sphagnum moss) are frequent and 

often abundant. Other frequent species include Carex folliculata (follicled sedge), Lycopus 

uniflorus (horehound), Thelypteris palustris (marsh fern), and Osmunda regalis (royal fern). 

Betula alleghaniensis (yellow birch) was frequent only at some Locke Pond and Barrington 

samples, while absent from other samples. Symplocarpus foetidus (skunk cabbage) is restricted 

to this and the other coastal types described below. 

Some examples classified to this type naturally occur in seasonally flooded settings while 

others may be undergoing a shift in composition towards this type as a result of raised water 

levels from beavers or human impoundments. For instance, Locke Pond is controlled by a 

spillway, and Newton Cedar Swamp has a beaver dam at its outlet recently bolstered by a 

landowner. However, additional information on historic patterns of water levels would be useful 

to confirm this. Atlantic white cedar in seasonally flooded settings may be more vulnerable to 

flood extirpation than those with more isolated hydrologies. This contention may be supported 

by pollen core evidence (albeit slimly) where cedar has been present in an hydrologically stable 

basin (not seasonally flooded) for 4,000 years in Antrim (Belling 1977). Situations that are more 

susceptible to hydrologic or other alterations may not have a similar long-term viability. The 

cedar in Fairhill swamp in Rye, for instance, has recently declined due to flood or salt 

inundation. Pollen core studies from this swamp indicate that cedar has only been present for 

some 400 years (Belling 1977). 

Although all plots classified as the seasonally flooded type occur in the near coastal zone, it 

is likely that a boreal seasonally flooded type also exists. One plot from Ring Brook Swamp 

(near the Brook) in Sutton had 4 species characteristic of the seasonally flooded type and may 

best be considered as a boreal seasonally flooded type. Many small remnant cedar populations 

occur in seasonally flooded habitats, but are not considered good examples of the vegetation type 

itself. This type is apparently similar to Motzkin's (1991) seasonally flooded type. 

Measurements of pH were generally among the highest recorded for cedar swamps in New 

Hampshire with a range of 4.4 to 6.5 (average 5.4, n=8; without highest pH of 6.5 possibly 

affected by external factors the average is 5.2). Elevation ranged from 30 ft. to 250 ft. for the 

coastal examples. 


• Seasonally flooded red maple swamp (S4S5) 

Acer rubrum/Carex stricta and Acer rubrum/Calamagrostis canadensis seasonally flooded swamps 

This is a common type of red maple swamp associated with stream drainages that are 

seasonally flooded, particularly along low gradient sections of first, second, or third order 

streams (less commonly 4th). Soils are typically alluvial or are shallow mucks or peat over 

alluvial mineral soils. These differ from floodplain forests by a seasonally rather than 

temporarily flooded water regime, and lower energy environments that allow the development of 

organic or organic rich soils as opposed to mineral soils with no organic horizon. They are 

commonly successional from wet meadows or shallow emergent marshes and have either a 

woodland or forest canopy structure. Acer rubrum (red maple) is the primary or sole tree 

species, and the shrub layer may be absent to moderately dense depending on the successional 

sequence. Clonal graminoids such as Carex stricta (tussock sedge) and Calamagrostis 

canadensis (blue-joint) are the most frequent dominants. Numerous other wetland herbs of 

marshes and swamps may be present. Although this is a common swamp type it has not been 

well sampled. 

• Seasonally saturated red maple swamp (S3S4) 

Acer rubrum/Symplocarpus foetidus-Veratrum viride seasonally saturated swamp 

Red maple swamps along small drainages of 1st or 2nd order streams that are typically 

saturated early in the season but dry up later in the season fall into this category (based on NH 

Heritage field surveys and Golet et al. (1993)). Overland runoff, lateral subsurface flow, and 

perhaps seasonal groundwater flow may contribute water to these swamps seasonally, but 

significant perennial groundwater seepage is absent and surface water is temporary or absent 

unlike in saturated or seasonally flooded swamps (see seepage swamps above for swamps in 

similar landscapes with more persistent seepage). These swamps have not been well sampled 

but probable characteristic species include red maple with lesser quantities of a variety of mesic 

site hardwoods and conifers, Symplocarpus foetidus (skunk cabbage), Veratrum viride 

(hellebore), Viola spp. (violets), Osmunda cinnamomea (cinnamon fern), Spiraea latifolia 

(meadow-sweet), and Arisaema triphyllum (Jack-in-the-pulpit). 

• Seasonally flooded boreal swamp (SU) 

Abies balsamea/Alnus incana seasonally flooded swamp 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This is a broadly defined and very poorly 

sampled group of swamps. It is questionably distinct from red spruce swamps described 

elsewhere, but deserves field survey to determine distinctiveness. Boreal conifers, tall shrubs, 

and herbs of alluvial wetlands dominate in stream or lakeside positions that are subject to 

seasonal over-bank flooding. They are presumably successional from marshes in abandoned 

beaver meadows of northern regions. 


SOILS/GEOLOGY/HYDROLOGY: Seasonally flooded water regime with mineral or shallow organic 

soils. 

CHARACTERISTIC VEGETATION: Potential trees include Picea rubens (red spruce), Picea mariana 

(black spruce), Abies balsamea (balsam fir), Acer rubrum (red maple), and Populus balsamifera 

(balsam poplar). Alnus incana var. americana (speckled alder) is the most likely dominant 

shrub, although others may be present in some abundance including Spiraea alba var. latifolia 

(eastern meadow-sweet), Cornus sericea (red osier dogwood), Lonicera villosa (hairy 

honeysuckle), and Rubus pubescens (dwarf raspberry). Herbs are likely to include 

Calamagrostis canadensis (blue-joint), Carex stricta (tussock sedge), Carex lacustris (lake 

sedge), Carex trisperma (three-seeded sedge), and Osmunda regalis (royal fern). Sphagnum 

moss is probably in moderate to low abundance due to the broadly fluctuating water levels. 

DISTRIBUTION: North of and including the White Mountains. 

COMMENTS: This swamp has more significant seasonal water fluctuations than northern 

hardwood-black ash-conifer seepage swamps and red spruce-Sphagnum swamps described 

elsewhere, but the differences in species composition needs to be substantiated with additional 

field observations. This community may represent a later-successional expression of Alnus 

incana basin/seepage shrub thickets (this shrub thicket is similar floristically but has a less dense 

tree canopy component). 

GOOD EXAMPLES: Margins of Androscoggin River (Errol); south of First Connecticut Lake. 

SOURCES: Limited NH Heritage surveys. 

TEMPORARILY FLOODED/SEASONALLY SATURATED FLOODPLAIN AND TERRACE FORESTS 

Floodplain forests are natural communities that occur on mineral soils on periodically 

flooded bottomlands associated with river corridors. Historically, these natural communities 

have been fragmented and impacted by agriculture, timber harvesting, and other human activities 

associated with development. Regionally, floodplain forests are imperiled and many natural 

community types are rare. 

Low floodplain forests associated with New Hampshire’s major (fourth-order and higher) 

rivers (Bechtel and Sperduto 1998) are typically dominated by Acer saccharinum (silver maple) 

and/or Acer saccharum (sugar maple). Significant stretches of floodplain forest also occur on 

third-order rivers in New Hampshire. These floodplain forests, frequently dominated by Acer 

rubrum (red maple) and other tree species, have statewide significance and form an integral part 

of wetland corridors of smaller rivers. 

The descriptions below include both floodplain forests (low, medium, and high) and terraces 

at higher elevations above the channel. Most low floodplain forests flood approximately every 

one to three years. We also describe some medium and high floodplain forests with longer flood 

return intervals, although these communities were not sampled as comprehensively as the low 

floodplain forests. In this report, “terrace” is used to describe inactive floodplains that are 


essentially isolated from riverine influences. Compared to the floodplain forests at lower 

elevations above the river channel, terraces are characterized by probable flood intervals of more 

than 100 years, a flora reflecting this longer flood return interval, increased soil horizon 

development, and other environmental processes that suggest an inactive floodplain. 

Floodplain forests are diverse ecosystems that occur at the interface between the aquatic and 

terrestrial environments of valley bottoms. All floodplain forests are periodically flooded by a 

river, although with varying frequencies and intensities. Several authors have defined a river’s 

floodplain as the area flooded every one to three years, specifically when the river exceeds its 

bankfull discharge, which is the highest level water reaches prior to spilling over the riverbank 

(Rosgen 1996; Dunn and Leopold 1978). Some studies suggest a range of flooding frequency 

between one and 25 years, however, depending on how the “active floodplain” (the area flooded 

regularly) and the abandoned “low terrace” floodplain are defined (Rosgen 1996). These 

definitions rely on the assumption that floodplains are site-specific terrestrial locations along a 

river corridor that happen to receive floodwaters. Other authors consider how species adapt to 

variable flood pulses within the entire "aquatic/terrestrial transition zone," or the linear area 

along the entire river corridor, regardless of river order (Junk et al. 1989). 

It is widely accepted that flood frequency, duration, and intensity are the primary factors 

influencing floodplain dynamics (Dollar et al. 1992). As river waters rise, sediment is 

transported downstream and deposited where water slows and spreads out in floodplains 

(Wistendahl 1958; Jorgenson 1978). Coarse sediments fall out along main channel edges and 

form natural sandy levees, while finer, silty sediments settle on flat higher floodplains. Mixing 

and churning flood waters can create a mosaic of different soil conditions and microtopography 

within a single site (Bornette and Amoros 1996; Hupp 1986; Hupp and Osterkamp 1985; Barnes 

1978), as well as a mosaic of different sites along a single river (Osgood 1996; Shankman 1993). 

Common life history strategies of herbaceous species in floodplains include spreading by 

rhizomes (e.g., some nettle species), growing in perennial rooted clumps (e.g., Matteuccia 

struthiopteris var. pensylvanica (ostrich fern) and some grass species), and having high numbers of 

wind- or water-dispersed seeds (e.g., many annual plants). Hardin and Wistendahl (1983) found 

that "the distribution patterns of perennials were related primarily to . . . vegetative reproduction. 

There was consequently greater heterogeneity in distribution of perennials over the stand." 

Rare species documented from floodplain forest and adjacent oxbow marsh habitat include 

Cardamine bulbosa (bulbous bitter-cress; S1), Allium canadense (wild garlic; S1), Bidens 

discoidea (small bidens; S3), Mikania scandens (climbing hempweed; S2), Sparganium 

eurycarpum (giant bur-reed; S2), Calamagrostis pickeringii (Pickering's reed bent-grass; S2S3), 

Carex cristatella (small crested sedge; S2), Carex seorsa (separated sedge; S1), Acer nigrum 

(black maple; S1), and Betula nigra (river birch; S2). 


FLOODPLAIN FORESTS OF MAJOR RIVERS 

SILVER MAPLE FLOODPLAIN FORESTS 

Two silver maple floodplain forest types are distinguished from red and sugar maple 

dominated floodplain forests in several ways, and collectively represent the classic floodplain 

forest type on large rivers in New Hampshire. Soils are highly variable, ranging from well 

drained coarse sand on levees, to poorly drained soils in low terraces and floodplain oxbow 

pools. The most common soil series mapped by the Natural Resource Conservation Service 

include Scarboro, Rumney, Rippowam, Ondawa, Occum, Pootatuck, and Podunk (very) fine 

sandy loams; Winooski and Saco silt loams; Suncook loamy (fine) sands; various bottomland or 

riverwash categories, various mucks and peats; and complexes of various types. Average shrub 

and sub-canopy tree dominance is low, while the total number of woody species is similar to the 

species richness in sugar maple types. Average percent herb cover is similar to red maple types, 

while canopy closure (average % cover of woody species) is relatively low compared to other 

types. Average species richness for herbaceous species is intermediate, while woody species 

richness is low compared to other broad groups. Classic floodplain vines (e.g., river grape (Vitis 

riparius) and others) are more common in this broad group, occurring mostly in canopy gaps and 

along edges. Although the two types described below are similar in their canopy structure, 

herbaceous species and floristic patterns are distinct. 

• Silver maple/wood nettle-ostrich fern floodplain forest (S2) 

Acer saccharinum/Laportea canadensis-Matteuccia struthiopteris floodplain forest 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This is one of two distinct floodplain forest 

community types dominated by a mature Acer saccharinum (silver maple) canopy. These 

riparian forests are often associated with a confluence between the mainstem river and a 

tributary, however many low floodplain terraces develop along river meanders, or other slow 

moving areas of the river course. This type receives floodwaters on nearly an annual basis, with 

climate and river regulation being the primary control over the periodicity and intensity of 

floods. They probably have peak floods in spring associated with melt-waters from the White 

Mountains and other mountainous areas. Primarily found along large rivers, this lower terrace 

type is characterized by deep alluvial, silty soils that are deposited when flood waters exceed 

their banks and drop finer sediments in the slow-moving, pooled water that spreads across the 

broader floodplain. Within site slough channel drainages can be up to two meters deep, creating 

small, rapidly draining streams that may support marshy vegetation soon after floodwaters 

recede. There is a high degree of microtopographic variation, with sand levees near the river's 

edge, riparian vernal pools, soil depressions surrounding large tree trunks, and sloughs. On a 

larger scale, the floodplain forest floor is a flat alluvial terrace, with occasional higher terraces 

that are transitional to upland. Most of these higher flat terraces have been converted to 

agricultural land or other development. 

On average, the silver maple/wood nettle-ostrich fern floodplain forest has nearly twice the 

percent coverage of forbs (contributing to a higher total herb cover), as well as the highest fern 


coverage compared to other floodplain natural communities, while its graminoid, shrub, and subcanopy 

tree coverage is low, especially compared to red maple floodplain forests. 

SOILS/GEOLOGY/HYDROLOGY: This type is found primarily along the Connecticut River, 

although it occurs on smaller watersheds as well. There is a high degree of microtopographic 

variation on these well-developed floodplain terraces. Soils are generally somewhat poorly 

drained to moderately well drained silt loams or very fine sandy loams. Due to the dynamic 

nature of flooding and almost yearly deposition of new soil material, soil horizon development is 

virtually absent, except on higher terraces. Organic debris from leaf litter and flood wash is 

occasionally buried under new silt and sand deposits creating layers or lenses of slowly 

decomposing organic matter, interspersed with either orange-red mottled sediments, or pure gray 

silt. Soil pHs range widely (average pH=5.7), but are more basic in examples found along the 

Connecticut River watershed, perhaps due to the more basic bedrock associations upstream. 

Watershed size varies widely, but most examples are found along the Connecticut River where 

upstream basins exceeds 2,000 mi 2 . 

CHARACTERISTIC VEGETATION: The tree layer is uniformly dominated by Acer saccharinum 

(silver maple), with Fraxinus americana (white ash), Ulmus americana (American elm), and 

Populus deltoides (eastern cottonwood) present in varying degrees. Celtis occidentalis 

(hackberry)* and Juglans cinerea (butternut) sometimes occur in Connecticut River examples, 

especially along the river or upland edge. Similar tree species are usually growing in the subcanopy, 

however shrubs and vines grow only along edges or in recent gaps created by natural or 

human-induced disturbance. A rich, thick carpet of herbaceous growth under the over-arching 

canopy creates an open, high ceiling cathedral-like appearance in most examples. The herb layer 

is dominated by patches of pure Matteuccia struthiopteris var. pensylvanica (ostrich fern) and 

Laportea canadensis (wood nettle), both of which can grow 1.8 m (6 ft.) tall, and to the 

exclusion of many other herbs. Other herbaceous and vine species usually present, but never 

dominant, include Onoclea sensibilis (sensitive fern), Athyrium filix-femina var. angustum 

(northern lady fern), Cinna arundinacea (common woodreed), Boehmeria cylindrica (false 

nettle), Impatiens capensis (spotted touch-me-not), Thalictrum pubescens (tall meadow-rue), 

Arisaema triphyllum (Jack-in-the-pulpit), Parthenocissus quinquefolia (Virginia creeper), 

Eupatorium maculatum (spotted Joe-pye-weed). The rare Arisaema dracontium (green dragon)* 

is found along the Connecticut River at some sites in low floodplain terraces among ostrich fern. 

Shrub layer is typically poorly developed or absent. 

DISTRIBUTION: Examples are primarily along the Connecticut River, with others along the 

Merrimack, Saco, and Dead Diamond River. The largest, most mature and best-developed 

examples are along the Connecticut River mainstem. Those along the Saco and Dead Diamond 

tend to be marginal and small relative to upper terrace forests. 

COMMENTS: Like all floodplain forest natural community types, this "classic" large river type 

can be found throughout the state, and associated with any of the other types described here. The 

best examples are large (>30 acres), with other associated communities along the edges or on 

higher terraces. 


GOOD EXAMPLES: Bedell Bridge State Park, Howard Island, Cheshire County Site, portions of 

the Technical Institute floodplain. 

SOURCES: NH Heritage field surveys 

• Silver maple/false nettle-wood reed-sedge floodplain forest (S2) 

Acer saccharinum / Boehmeria cylindrica-Cinna-Carex floodplain forest 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This type is very similar to the silver maple / 

wood nettle-ostrich fern floodplain forest, but is distinguished by sandier soil, more diverse 

ground cover, and tendency to occur on more medium sized rivers, in addition to its large river 

fidelity. Over-arching Acer saccharinum (silver maple) characterizes this type, with Ulmus 

americana (American elm) in association. A lack of Fraxinus americana (white ash), Celtis 

occidentalis (hackberry), and Juglans cinerea (butternut) hint at the more acidic nature of the 

soils in this type. Herb species diversity and richness is higher and more variable in this type as 

well. While flooding intensity and frequency is probably comparable in both two silver maple 

types, this type may be characterized by shorter duration, higher disturbance floods in some 

examples. While physical characteristics and landscape position are similar, this type is mostly 

distinguished by its distinct floristic character. 

Forest patch sizes ranging from 30 acres to as small as 3 acres. Small patches have 

considerable edge area, either from upslope edges, forest canopy gaps, or from river-edges, 

which increases edge to interior ratios, effectively reducing the area of interior forest unaffected 

by "edge effect." 

This type has a distinctly higher graminoid % cover and higher total herb species richness 

than the silver maple/wood nettle-ostrich fern floodplain forest, while having the lowest tree 

species richness. Forb total species richness per plot is higher than in the silver maple/wood 

nettle-ostrich fern floodplain forest, reflecting the variability of species found within this type, 

but the lower average species richness reflects fewer species encountered from site to site. 

SOILS/GEOLOGY/HYDROLOGY: Soils are highly variable, ranging from somewhat poorly drained 

silt loams to well drained sandy loams. Soil pHs tend to be slightly acidic (average pH=5.3), 

perhaps related to acidic upstream bedrock in these eastern drainage basins. Although variable, 

this type is found on rivers with drainage basins less then 1,000 mi 2 in area above site locations, 

with some Merrimack River examples with basin areas approaching 2,000 mi 2 . Microtopographic 

variation is similar to the silver maple/wood nettle-ostrich fern floodplain forest. 

CHARACTERISTIC VEGETATION: The tree layer is dominated by a nearly pure cover of Acer 

saccharinum (silver maple), with Ulmus americana (American elm) as a subcanopy associate. 

Spiraea alba (meadow-sweet) and Cephalanthus occidentalis (buttonbush) occur on drier and 

wetter edges (respectively), especially along the Contoocook and medium river examples. The 

herb layer is characterized by a notable lack of Laportea canadensis (wood nettle), and a 

predominance of Boehmeria cylindrica (false nettle). Onoclea sensibilis (sensitive fern) is 

usually dominant, with Matteuccia struthiopteris var. pensylvanica (ostrich fern) present in 


considerable amounts. Toxicodendron radicans (climbing poison ivy) is prevalent in this type, 

whereas it is only occasionally present in the above type. Other forbs are similar to the above 

type, but graminoid species presence, richness and diversity are all higher in this type, with 

species such as Cinna arundinacea (common woodreed), Cinna latifolia (drooping woodreed), 

Carex crinita (drooping sedge), Leersia virginica (Virginia cut-grass), and Carex intumescens 

(inflated sedge). The dominance by false nettle and the presence of woodreed are diagnostic of 

this type; however, there is some species occurrence overlap between the two silver maple types. 

The shrub layer is generally absent, except on edges and canopy gaps. 

DISTRIBUTION: Examples are from Merrimack River and various medium sized rivers 

throughout the state. 

COMMENTS: This can be considered the typical silver maple floodplain forest type for New 

Hampshire; it is mostly distinguished from other floodplain forests by differences in herbaceous 

species (higher species richness, diversity), more acidic soils, and association with smaller rivers. 

GOOD EXAMPLES: Characteristic examples include Merrimack River State Forest, NH Technical 

Institute, Campton WMA, along the Ashuelot River near Keene Airport, Franklin Falls, 

Contoocook River. 

SOURCES: NH Heritage field surveys; Osgood (1996) 

SUGAR MAPLE FLOODPLAIN FORESTS 

Two sugar maple floodplain forest types are distinguished primarily by sugar maple dominance, 

or by sugar maple presence in the overstory with silver maple as a codominant canopy species. The 

sugar maple floodplain group average percent canopy cover is higher than the red and silver maple 

types, while its total herb dominance is lowest among the three groups. However, within plot 

species richness tends to be fairly high compared to other types, perhaps resulting from this natural 

community's transitional nature to upland forests at some sites; from lower flood frequency, but 

higher flood intensity, or other factors. These species patterns may also be influenced by 

occasional enriched conditions at these sites. Vine, shrub, graminoid, and subcanopy dominance 

are all similar to the silver maple types, while fern cover is lowest compared to other types. 

• Sugar maple/ironwood/short husk floodplain forest (S1) 

Acer saccharum / Ostrya virginiana / Brachyelytrum erectum floodplain forest 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This community occurs within the low 

floodplain terrace of more northern rivers. Flood regulation is less common on these rivers. The 

high gradient river basins and strong pulse flood regime characteristic of these rivers leads to 

high disturbance, short duration flooding events. Plant associations are similar to upland forests, 

but show considerable evidence of periodic, high intensity flood events that may only 

temporarily disrupt plant growth. Distinct variations of this type include northern floodplain 

terraces with northern softwood tree species among the hardwoods. 


This natural community is distinguished by a relatively high canopy tree dominance (average 

percent cover). Enriched soils at some sites on slightly elevated terraces (and resulting reduced 

flood disturbance) may be contributing factors that favor tree dominance. This type has the 

lowest fern dominance of any floodplain forest natural community, while dominance by other 

upland forbs and grasses is similar to other floodplain forests. 

SOILS/GEOLOGY/HYDROLOGY: Soils are generally alluvial, often showing buried organic layers 

and fresh sandy alluvium. The upper 15-50 cm of soil was usually finer textured than underlying 

soil, with a loamy fine sand/fine sandy loam over loamy sand, sand, or less frequently 

gravel/cobble. Soil pHs consistently ranged from 5.0-5.4 in the top 50 cm, attesting to the more 

acidic bedrock upstream. The Soil Conservation Service has mapped this forest type primarily 

into the Suncook and Ondawa (sandy subsoil variant) series. In several examples the Colton 

series and typical Ondawa low bottom are the dominant soil types, attesting to wide variety of 

soil textures and drainage tendencies associated with this floodplain type (somewhat poorly to 

well drained). For example, at one site, one might encounter slightly elevated terraces with 

considerable soil horizon development next to pure sand deposition surrounding a pure silt low 

terrace that borders a scoured cutbank. The high variability of flooding intensity and frequency 

creates multiple microhabitats within sites, and a highly random probability of long-term 

survival for plants of all types. Evidence of high energy flood pulses include steep river banks, 

coarse sand deposition, cobble-lined slough channels, patches of cobbles supporting early 

successional woody vegetation along river edges, and occasional piles of dead woody debris. 

CHARACTERISTIC VEGETATION: The vegetation structure and composition was quite consistent 

for these maturing (65-100 year-old), second-growth forests. The 20-25 m tall, closed tree 

canopy is dominated by Acer saccharum (sugar maple) and Quercus rubra (red oak), with 

Fraxinus americana (white ash) and Pinus strobus (white pine; sometimes as supercanopy) of 

secondary importance. Occasionally Tilia americana (basswood), Acer saccharinum (silver 

maple), Acer rubrum (red maple), and others occur in the canopy. The subcanopy is variable in 

height and abundance, but consistently has sugar maple and Ostrya virginiana (ironwood) as the 

principal species. Shrubs are generally not dominant, except at edges. Compared to average 

northern hardwood forests, the herb layer is often more lush – commonly with a high total 

coverage. The most abundant, and/or common, species found were: Solidago caesia (bluestemmed 

goldenrod), Uvularia sessilifolia (sessile-leaved bellwort), Toxicodendron radicans 

(climbing poison ivy), Aralia nudicaulis (wild sarsaparilla), Carex pedunculata (long-stalked 

sedge), and Brachyelytrum erectum var. glabratum (northern short husk grass). The abundance 

of Solidago caesia (blue-stemmed goldenrod) and Brachyelytrum erectum var. glabratum 

(northern short husk grass) was the most floristically unique aspect in this forest type. A 

naturalized grass, Poa nemoralis (wood bluegrass), also occurred quite frequently. The rare 

Teucrium canadense var. virginicum (Canadian germander)* is found along medium height 

terraces along these floodplains on the Saco River. Overall, the composition of this type 

suggests somewhat drier conditions than other floodplains. 


Other examples of this community type were characterized by decreased importance of sugar 

maple and the increased importance of Quercus rubra (red oak), Tsuga canadensis (hemlock), 

and Fagus grandifolia (American beech). These also had a notable lack of herb cover, with 

species composition tending towards that found in acid woods. Furthermore, the soils at these 

mixed woods sites tended to be coarser (loamy sands over sands and gravel), and hence drier. 

DISTRIBUTION: This forest type occurred along the entire length of the Upper Saco River as well 

as along moderately sized northern rivers. 

COMMENTS: This type may be considered the typical floodplain type for the upstream reaches of 

rivers, especially those that cascade from mountainous terrain. 

GOOD EXAMPLES: The upper reaches of the Saco River, between Bartlett and Conway, features 

this type. 

SOURCES: NH Heritage field surveys; description adapted from Engstrom (1997). 

• Sugar maple-silver maple-white ash floodplain forest (S1S2) 

Acer saccharum-Acer saccharinum-Fraxinus americana Floodplain Forest 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This community type of northern rivers is 

transitional between pure silver maple floodplain forests and the sugar maple/ironwood/short 

husk floodplain forest. It shares some floristic associations of both communities, but it is not 

clearly one or the other. Floristically it is distinct, even though landscape features may not be the 

same throughout. It generally has the same structural features, with over-arching hardwoods and 

a fern and forb understory with few shrubs. It is found either along the river's edge or along 

terraces far from the river, but is flooded during spring runoff. Soils are variable, and in some 

cases an enriched herb layer hints at higher pH values. 

Structural patterns are similar to sugar maple/ironwood/short husk floodplain forests, with 

the exceptions of a lower canopy tree dominance and a higher fern dominance. Total and 

relative species richness values are similar for both sugar maple types. 

SOILS/GEOLOGY/HYDROLOGY: Soils are variable, but tend to be well to moderately well drained 

sandy loams along northern riverside examples, and somewhat poorly drained silty loams in the 

back channel landscape position at southern examples. Soils are slightly enriched in some cases, 

but not as basic as the silver maple/wood nettle-ostrich fern floodplain forest. The back-channel 

examples have little microtopographic variation, instead forming broad flat terraces that may be 

lower in elevation than the surrounding landscape; with features suggesting an abandoned river 

channel. Northern examples are on higher terraces similar to the sugar maple/ironwood/short 

husk floodplain forest, with evidence of high intensity flood pulses. 

CHARACTERISTIC VEGETATION: Acer saccharinum (silver maple) and Acer saccharum (sugar 

maple) share canopy dominance with Fraxinus americana (white ash). The presence of ash is 

diagnostic and may be related to the somewhat enriched condition of soils of this type. Prunus 

serotina (black cherry) is present in some higher terrace examples, Ulmus americana (American 


elm) occasionally grows in the sub-canopy, with occasional northern hardwood species, 

including Betula alleghaniensis (yellow birch). Toxicodendron radicans (climbing poison ivy) is 

a common vine, while Brachyelytrum erectum var. glabratum (northern short husk grass) and 

Carex intumescens (inflated sedge) are common graminoids. Diagnostic ferns of the pure silver 

maple types – Onoclea sensibilis (sensitive fern) and Matteuccia struthiopteris var. pensylvanica 

(ostrich fern) – hint at affinity with the "classic" large river floodplain types; however, herbs, 

including Uvularia sessilifolia (sessile-leaved bellwort), Maianthemum canadense (Canada 

mayflower), Smilacina racemosa (false Solomon's seal), and Aster divaricatus (white wood 

aster), are more commonly found in upland northern forests. Rich woods indicator herbs, 

including Arisaema triphyllum (Jack-in-the-pulpit) and Caulophyllum thalictroides (blue cohosh) 

are also occasionally present, especially in sites with primarily sugar maple canopies. These 

patterns, as well as the presence of graminoids, indicate a distinct, albeit transitional type 

between silver maple and upland/sugar maple floodplain forests. 

DISTRIBUTION: Found along mostly central and northern rivers with high energy and chaotic 

flood regimes. The back terrace type is found as far south as Concord, on the Merrimack, but it 

is primarily found along the Saco and Androscoggin drainages. 

COMMENTS: This type shows transitional characteristics between silver maple floodplain forests 

and upland forest types, occasionally with rich indicator plant species. 

GOOD EXAMPLES: Campton WMA island, various Saco River sites. 

SOURCES: NH Heritage field surveys 

FLOODPLAIN AND TERRACE FORESTS OF THIRD AND SOME FOURTH-ORDER RIVERS 

Red maple is a common component in the tree canopy of all the forested floodplain 

community types described below. The range of natural communities that may be present on a 

floodplain is most likely a result of relative height above the river, distance from the river, and 

the length of time since the river last flooded or altered its course away from its former channel. 

Floodplain communities that may form a mosaic with red maple dominated or co-dominated 

forested floodplains include oxbow marshes and ponds, riverside meadows and emergent 

marshes, sand and gravel barrens, vernal pools, shrub thickets, and other forested floodplain 

community types. These floodplain community mosaics are hydrologically similar to those 

occurring with silver maple dominated floodplain forests in that both are profoundly influenced 

by spring over-bank floods. However, red maple dominated or co-dominated floodplain forests 

and associated floodplain communities along large streams and minor rivers probably differ 

hydrologically from their silver maple counterparts along major rivers by (1) reduced flood 

intensity, (2) typically shorter flooding periods, and (3) flooding that may occur earlier in the 

year. 


FORESTS ON CIRCUMNEUTRAL SOILS 

• Swamp white oak floodplain forest (S1) 

Quercus bicolor-Acer rubrum/Carpinus caroliniana floodplain forest 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: Floodplain forests dominated or co-dominated 

by Quercus bicolor (swamp white oak) are apparently state and regionally rare. In New 

Hampshire, they are restricted to within 50 km (30 miles) of the coast and are associated with 

heavy (silty) soils of marine or recent floodplain origin. Swamp white oak, Fraxinus 

pennsylvanica (green ash), other species indicative of moist, fertile conditions are diagnostic of 

this type. The species composition and nutrient levels are most similar to the basswood-white 

ash-black maple floodplain. Betula nigra (river birch)* is rare in New Hampshire, but is 

codominant with swamp white oak in several floodplain forests along tributaries of the lower 

Merrimack River. Two variants are described based on floristic differences associated with 

elevation above the river channel. A third variant is described based on the abundance of Betula 

nigra (river birch). 

SOILS/GEOLOGY/HYDROLOGY: Floodplains along three river systems ranged from 0.3-2 m (ca. 1- 

6 ft.) above the main river channel. The lower floodplain is somewhat poorly drained silt loam 

or fine sandy silt loam with a thin organic horizon (0-2 cm (0-0.8 in.)). Medium to high 

floodplain are somewhat poorly to moderately well drained with a similar soil profile. There is 

little or no hummock and hollow development. All examples occur at less than 45 m (150 ft.) 

elevation. Average pH is 5.4. 

CHARACTERISTIC VEGETATION: Both lower and higher floodplains are dominated by a mix of 

Quercus bicolor (swamp white oak) and Acer rubrum (red maple), with an understory of 

Carpinus caroliniana (musclewood), abundant Onoclea sensibilis (sensitive fern), and variable 

amounts of Viburnum dentatum var. lucidum (northern arrow-wood), Viburnum lentago 

(nannyberry), Ilex verticillata (winterberry), Smilax herbacea (glaucous carrion-flower), and 

Toxicodendron radicans (poison ivy). Fraxinus americana (white ash) is occasional. Carex 

laxiculmis (loose-stemmed sedge), an uncommon sedge restricted to silty soils in southern New 

Hampshire, is also found in this community. There is little or no moss cover. High and low 

floodplain forest examples are described as two variants, although a continuum of species 

composition change is evident across the elevation gradient at most sites. A third variant is 

described based on the abundance of river birch. 

The three variants are as follows: 

1. Swamp white oak floodplain forest, low variant: The lower floodplain has a 

moderately dense to dense (40-90%) herbaceous layer, a sparse to moderately dense 

shrub layer (6-40%), and a light to moderately dense seedling/sapling layer. Fraxinus 

pennsylvanica (green ash) is common to abundant, and apparently unique to this 

community among non-silver maple floodplain forest communities. Other species that 

are most frequent and abundant in swamp white oak floodplain forests include Carex 

crinita (drooping sedge), Cinna arundinacea (common woodreed), Thelypteris palustris 


(marsh fern), and Viburnum lentago (nannyberry). Other herbaceous species indicative 

of the low floodplain variant include Cornus amomum (silky dogwood) Carex stricta var. 

strictior (tussock sedge), Iris versicolor (blue flag), Lysimachia terrestris (swamp 

candles), and Ulmus americana (American elm). 

2. Swamp white oak floodplain forest, high variant: This variant corresponds with 

medium to high elevation floodplains. The herb layer is moderately dense (40-60%) and 

the shrub layer is moderately to very dense (30-80%). Tree seedling and sapling 

regeneration in the shrub layer is sparse. There is a greater abundance of upland tree, 

shrub, and herb species compared to the low floodplain variant. These include Carya 

ovata (shagbark hickory), Pinus strobus (white pine), Quercus rubra (red oak), Prunus 

serotina (black cherry), Ostrya virginiana (ironwood), Fagus grandifolia (American 

beech), Thelypteris noveboracensis (New York fern), Maianthemum canadense (wildlily-of-the-valley), 

Uvularia sessilifolia (sessile-leaved bellwort), and Vaccinium 

angustifolium (low bush blueberry). Among floodplain forests in New Hampshire, 

shagbark hickory is most frequent in this variant. 

3. Swamp white oak floodplain forest, Betula nigra (river birch) variant: All of the 

species indicative of the low floodplain forest variant (swamp white oak type) may occur 

in this variant. Red maple, swamp white oak, Tilia americana (basswood), Fraxinus 

americana (white ash), and Ulmus americana (American elm) are all common along with 

abundant river birch. Cardamine bulbosa (bulbous bitter-cress)* and Allium canadense 

(wild garlic)* are rare plants found in this type. This variant is most similar in species 

composition to the low floodplain forest variant and basswood-white ash-black maple 

floodplain forest community. 

DISTRIBUTION: Restricted to within 50 km (30 miles) of the coast in the Great Bay watershed 

(Exeter, Lamprey, and Powwow Rivers) and to tributaries of the lower Merrimack River (Beaver 

Brook and Spicket River). The river birch variant is restricted to the Beaver Brook and Spice 

River systems. 

COMMENTS: This community type is most similar to the basswood-white ash-black maple 

floodplain forest and low floodplain examples of the red maple floodplain forest community on 

fertile soils. The river birch variant may be regionally rare and deserves further research to 

determine its distinctiveness as a community type and its regional significance. 

GOOD EXAMPLES: The Exeter, Lamprey, and Powwow Rivers all contain good examples of the 

low and high floodplain variants. Beaver Brook and Spice River contain examples of the river 

birch variant. 



• Basswood-white ash-black maple floodplain forest (S1) 

Tilia americana-Fraxinus americana stream bottom floodplain forest 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This community occurs on narrow floodplains 

along several streams draining into Great Bay. Stream watersheds are generally less than three 

square kilometers (two square miles). These forests are flooded during spring runoff periods and 

perhaps during other peak floods. Hummock-hollow microtopography is absent, but boulders 

and stones may be occasional on the soil surface at some sites. A mixture of species indicative 

of mesic enriched sites, floodplains, and wetland habitats occur together to distinguish this 

community from the seepage swamps, rich mesic forests, and river floodplain forests with which 

it shares some characteristics. 

SOILS/GEOLOGY/HYDROLOGY: Soils are silty loams with very shallow or absent organic 

horizons. The water regime is typically somewhat poorly drained but ranges from moderately 

well drained to poorly drained in local areas. 

CHARACTERISTIC VEGETATION: Tilia americana (basswood) and Fraxinus americana (white 

ash) are the primary overstory dominants. In lower abundance or occasionally present are Acer 

saccharum (sugar maple), Carya ovata (shagbark hickory), Acer rubrum (red maple), Quercus 

rubra (red oak), and less frequently Acer nigrum (black maple)*. Although black maple is not 

present at all occurrences, it appears to be native to this habitat, and it is considered fairly 

diagnostic of the community. Plant species often found on floodplains and in other wetland 

communities that are typically common in this community include Carpinus caroliniana 

(musclewood), Ulmus americana (American elm), Cornus amomum (silky dogwood), Viburnum 

lentago (nannyberry), Toxicodendron radicans (poison ivy), Thalictrum pubescens (tall meadow 

rue), Onoclea sensibilis (sensitive fern), Athyrium filix-femina (lady fern), Boehmeria cylindrica 

(false nettle), Impatiens capensis (jewelweed), Ludwigia palustris (water purslane), and Solidago 

rugosa (rough goldenrod). Several of these plant species are also indicative of soils with higher 

base status. Other characteristic species are Aster divaricatus (white wood aster) and less 

frequently Laportea canadensis (wood nettle), a species of rich alluvial sites. 

Non-native and sometimes invasive plant species are often present due to the proximity of 

floodplain habitats to agricultural fields, pastures, and a generally fragmented coastal landscape. 

These include Rhamnus cathartica (common buckthorn), Berberis vulgaris (European barberry), 

Berberis thunbergii (common barberry), Lonicera morrowii (Morrow's honeysuckle), Rosa 

multiflora (multiflora rose), Plantago major (common plantain), and Sedum spp. (sedum). 

DISTRIBUTION: Presently known only to occur along several streams with small watersheds 

draining into Great Bay. 

GOOD EXAMPLES: Great Bay Wildlife Management Area (Greenland). 

SOURCES: NH Heritage field surveys; Nichols and Sperduto (1997). 


• Rich sugar maple-ash-oak-hickory forest (S1) 

Acer saccharum-Fraxinus-Quercus/Matteuccia-Toxicodendron radicans-Equisetum hyemale- 

Erythronium forest 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This community occurs on steep slopes or flats 

of river floodplains formed from lake-bottom sediments of former glacial lakes, marine intrusion 

sediments, or high floodplains of more recent formation. These sediments often have 

considerable silt content that contributes to greater fertility than coarser floodplain sediments. 

Some examples in the southern part of the state (Connecticut and Merrimack Rivers) exhibit a 

high diversity of tree species. Seeps are common on slope faces. Windthrow may be common 

on unstable steep slopes under-cut by river flow. Ice damage to trees from high spring runoff is 

evident on some infrequently flooded terraces. 

SOILS/GEOLOGY/HYDROLOGY: Soils tend to be deep, loamy, mesic and fertile (mesotrophic to 

permesotrophic) and may occur on river terrace slopes or infrequently flooded terrace flats of 

recent or glacial lake-bed origin. Lakebed sediments vary from sands to silts and less frequently 

clays. Terrace slopes often have silt and clay layers that impede drainage and result in horizontal 

emergence of water (seeps) on steep banks. The variety of sediment textures and drainage 

classes on these slopes create a broad diversity of conditions for plant growth. Probable soil 

series are Unadilla, Suffield, Hartland, and Belgrade, all formed from glacio-lacustrine deposits 

(needs field confirmation). River terraces of frigid soils in the Mahoosuc-Rangley Lakes and 

Connecticut River subsections need further investigation. 

CHARACTERISTIC VEGETATION: A broad diversity of trees, up to 20 species at a site, may be found 

in some occurrences. This type is a narrowly defined enriched forest, apparently limited to warm 

southern or western exposures of steep lakebed sediments/river terrace slopes of the lower 

Connecticut and Merrimack River valleys. These forests have a southern or Appalachian 

character. Until differences can be substantiated, enriched forests of river terraces without 

southern species are presently not distinguished from typical rich mesic forest described elsewhere. 

This community probably supports a higher diversity of tree and other woody species than 

any other natural habitat in the state, which distinguishes this community from other enriched 

forests in New Hampshire (with the possible exception of some talus slopes). There is often a 

mix of species characteristic of floodplains, rich mesic forests, upland forests, and seeps. 

Tree species may include Acer saccharum (sugar maple), Fraxinus americana (white ash), 

Fraxinus pensylvanica (green ash), Tilia americana (basswood), Juglans cinerea (butternut), 

Tsuga canadensis (hemlock), Quercus rubra (red oak), Quercus alba (white oak), Carya ovata 

(shagbark hickory), Carya cordiformis (bitternut hickory), several Betula spp. (birches), Acer 

rubrum (red maple), Prunus serotina (black cherry), Ulmus americana (American elm), and 

others. Other more southern or Appalachian woody species include Cornus florida (flowering 

dogwood), Cornus rugosa (round-leaved dogwood), Carpinus caroliniana (musclewood), and 

Ostrya virginiana (ironwood). 


Nutrient-demanding understory species include Erythronium americanum (dogtooth violet), 

Asarum canadense (wild ginger), Matteuccia struthiopteris (ostrich fern), Hepatica americana 

(blunt-lobed hepatica), Hepatica acutiloba (sharp-lobed hepatica), Adiantum pedatum 

(maidenhair fern), Dicentra cucullaria (Dutchman's breeches), Asplenium platyneuron (ebony 

spleenwort), and Caulophyllum thalictroides (blue cohosh). Some examples along the 

Connecticut River harbor the rare Staphylea trifolia (bladdernut)* and Hydrophyllum 

virginianum (Virginia waterleaf)*. 

Other frequent and characteristic species include Onoclea sensibilis (sensitive fern), 

Toxicodendron radicans (poison ivy), Smilacina racemosa (false-Solomon's seal), 

Parthenocissus quinquefolia (Virginia creeper), Viburnum acerifolium (maple-leaved viburnum), 

Hamamelis virginiana (witch hazel), and Alnus incana var. americana (speckled alder). 

Groundwater emergence is often evident on the slope face above restrictive sediment layers or at 

the base of the terrace slope, supporting forest seep vegetation including Equisetum hyemale 

(scouring rush), Carex scabrata (rough sedge), Chelone glabra (turtlehead), Impatiens capensis 

(jewelweed), and other seep indicators. 

DISTRIBUTION: Valley bottom sediments of river terraces formed from glacial lake bottom 

sediments along southern and central reaches of major rivers (and possibly along coastal rivers) 

of Vermont Upland, Connecticut River, Coastal Plain, and Coastal Lowlands subsections. 

COMMENTS: Reasonably distinct and narrowly defined. More data are needed to substantiate 

differences between this type and rich mesic forests on till, river terraces, and lake sediments 

from various geographic locations in the state, including river terraces of the Vermont Upland 

subsection and frigid soils in the Mahoosuc-Rangley Lakes and Connecticut River subsections. 

GOOD EXAMPLES: Riverbluff below Conservation Center (Concord); riverbluff above Vernon 

Dam (Hinsdale); Dunshee Island (Cornish); part of Bedell Bridge State Park (Haverhill). 


FORESTS ON SUBNEUTRAL TO CIRCUMNEUTRAL SOILS 

• Red maple floodplain forest (S2S3) 

Acer rubrum floodplain forest 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This natural community can be found along 

major streams and minor rivers and on floodplains of major rivers above low floodplain forests 

dominated by Acer saccharinum (silver maple). Where Acer rubrum (red maple) dominates on 

the low floodplain, river channels are typically 6-30+ m (20-100+ ft.) wide with average summer 

water depths of 0.6-0.9+ m (2-3+ ft.). Small to moderate sized watersheds are typical above red 

maple dominated floodplains. 

SOILS/GEOLOGY/HYDROLOGY: Soils are usually somewhat poorly drained fine sandy loams and 

silt loams with very shallow or absent organic horizons. pHs average 5.1. Soil surfaces may be 

temporarily inundated during spring flood events. Reddish mottles occur at an average depth of 


10 cm (4 in.) on the low floodplain to nearly 20 cm (8 in.) on the high floodplain. In contrast to 

most swamps, hummock-hollow microtopography is absent or poorly developed. 

CHARACTERISTIC VEGETATION: Acer rubrum (red maple) dominates the tree canopy, with 

varying but smaller contributions by other hardwood and softwood species. Tree canopy 

structure ranges from woodland (25-60% tree cover) to forest (>60% tree cover). Shrub cover is 

generally low to moderately well developed and can include Ilex verticillata (winterberry), 

Viburnum spp., Vaccinium corymbosum (highbush blueberry), and others. The herb layer is 

most often well developed with a relatively high cover of ferns including Onoclea sensibilis 

(sensitive fern), Osmunda regalis var. spectabilis (royal fern), Athyrium filix-femina var. 

angustum (northern lady fern), and lesser amounts of Thelypteris spp. (fern), Osmunda 

cinnamomea (cinnamon fern) and Osmunda claytoniana (interrupted fern). The species 

composition of three variants is described below. Most of the species mentioned in the 

descriptions are not individually diagnostic of each variant, but each species assemblage as a 

whole is distinct. 

Three variants of this community are recognized: 

1. Red maple floodplain forest, low variant: Several environmental and floristic 

characteristics separate this variant from the medium/high variant and the more closely 

related low/medium variant. In the low red maple floodplain forest variant, the tree 

canopy is more open, graminoid cover and vine cover are higher, and depth to mottling is 

shallower than in the other variants. Examples typically occur at a lower floodplain 

elevation and closer to the river, giving this variant a wetter character. 

Acer rubrum (red maple) dominates the tree canopy. Infrequent tree species are 

Carya ovata (shagbark hickory), Pinus strobus (white pine), Quercus rubra (red oak), 

and others. Silver maple is usually absent or only found along the immediate river 

channel. Quercus bicolor (swamp white oak), if present, is in low abundance compared 

to its occurrence in swamp white oak floodplain forests. 

Plant species typical of wetter conditions distinguish this variant from the other two 

by their presence and/or higher cover, including Ulmus americana (American elm), 

Cornus amomum (silky dogwood), and Impatiens capensis (spotted touch-me-not). Other 

characteristic species are Rubus occidentalis (western black raspberry), Sambucus 

canadensis (common elderberry), Alnus incana var. americana (speckled alder), 

Parthenocissus quinquefolia (Virginia creeper), Vitis labrusca (fox grape), Apios 

americana (groundnut), Lycopus uniflorus (common water horehound), Boehmeria 

cylindrica (false nettle), Onoclea sensibilis (sensitive fern), Chelone glabra (white 

turtlehead), Oxalis stricta (showy yellow wood sorrel), Geum laciniatum (herb bennet), 

Geum canadense (white avens), and Galium asprellum (rough bedstraw). 

Common species that this variant shares with the closely related low/medium variant 

include Prunus serotina (black cherry), Viburnum dentatum var. lucidum (northern 

arrow-wood), Toxicodendron radicans (climbing poison ivy), Rubus hispidus (bristly 


dewberry), Dryopteris intermedia (intermediate wood fern), Athyrium filix-femina var. 

angustum (northern lady fern), Solidago rugosa (rough goldenrod), Thalictrum pubescens 

(tall meadow-rue), Arisaema triphyllum (Jack-in-the-pulpit), Carex intumescens (inflated 

sedge), Cinna latifolia (drooping woodreed), and Cinna arundinacea (common 

woodreed). Species frequently found in the other two variants but that are sparse or 

absent in the low red maple floodplain variant are Quercus rubra (red oak) and Viburnum 

nudum var. cassinoides (witherod). 

The low variant appears to be somewhat more transitional than the low/medium 

variant to open floodplain communities that occur immediately adjacent to the channel. 

Herbs, vines, and shrubs that reach their highest cover in open floodplain communities 

occur more frequently in the understory of this variant. They include Calamagrostis 

canadensis (blue-joint), Glyceria striata (manna-grass), Glyceria canadensis (rattlesnake 

manna-grass), Leersia oryzoides (rice cut-grass), Dulichium arundinaceum (three-way 

sedge), Carex stricta (tussock sedge), Carex lurida (sallow sedge), Carex scoparia 

(broom sedge), Agrostis capillaris (Rhode Island bent-grass), Poa pratensis (Kentucky 

bluegrass), Elymus virginicus (Virginia wild rye), Panicum clandestinum (deertongue), 

Solidago rugosa (rough goldenrod), Solidago gigantea (smooth goldenrod), Solidago 

canadensis (Canada goldenrod), Euthamia graminifolia (grass-leaved goldenrod), 

Eupatorium perfoliatum (perfoliate boneset), Eupatorium maculatum (spotted Joe-pyeweed), 

Eupatorium dubium (three-nerved Joe-pye-weed), Aster puniceus (purplestemmed 

aster), Asclepias incarnata var. pulchra (swamp milkweed), Bidens frondosa 

(common beggar-ticks), Clematis virginiana (virgin's bower), Spiraea alba (meadowsweet), 

Betula papyrifera (paper birch), and Polygonum hydropiper (water-pepper). 

2. Red maple floodplain forest, low/medium variant: This variant is closely related 

environmentally and floristically to the low red maple floodplain variant. Both variants 

may be found adjacent to the channel at relatively low floodplain elevations, although the 

low/medium variant can also occur at slightly higher elevations and at greater distances 

from the channel. 

Acer rubrum (red maple) dominates the tree canopy. Prunus serotina (black cherry), 

sparse to absent in the tree canopy on the high floodplain, is generally more common in 

this variant than in the low variant. Plant species most characteristic of this variant are 

Carpinus caroliniana var. virginiana (musclewood), Viburnum lentago (nannyberry), and 

Aster umbellatus (tall flat-topped white aster). Species frequently found in this variant 

and in higher floodplain areas, but that are sparse or absent in the low variant, are 

Quercus rubra (red oak) and Viburnum nudum var. cassinoides (witherod). Ulmus 

americana (American elm), Cornus amomum (silky dogwood), and Impatiens capensis 

(spotted touch-me-not), wetter site species common in the low variant, are somewhat less 

frequent in the low/medium variant and sparse to absent in the medium/high variant. 

Several plant species are characteristic of both the low and low/medium floodplain 

forest variants (see low variant description, second to last paragraph). 


3. Red maple floodplain forest, medium/high variant: Medium to high floodplain forests 

are similar to mesic, mixed hardwood-conifer forests of the transitional or central 

hardwood region, although some of them flood intermittently during peak floods 

(probably 5-100 year cycles). These forests are typically 0.3-0.9 m (1-3 ft.) higher above 

the river channel than the lower floodplain forests. Acer rubrum (red maple) is common 

in the tree canopy. Other tree species present in the lower red maple floodplain variants 

may frequently occur here as well with the exception of Prunus serotina (black cherry) 

and Ulmus americana (American elm), which are sparse or absent. Tree species that 

distinguish the higher floodplain from the lower floodplain by their presence and/or 

higher cover include Quercus rubra (red oak) and Pinus strobus (white pine). 

Shrubs with a higher fidelity to this variant compared to the two lower floodplain 

variants include Vaccinium corymbosum (highbush blueberry), Vaccinium angustifolium 

(early low blueberry), Gaultheria procumbens (wintergreen), Kalmia angustifolia (sheep 

laurel), Clethra alnifolia (sweet pepperbush), Ilex verticillata (winterberry), Hamamelis 

virginiana (witch hazel), and Gaylussacia baccata (black huckleberry). Viburnum 

nudum var. cassinoides (witherod) is frequent in this variant and the low/medium variant 

but is notably infrequent in the low variant. Shrubs that are absent or sparse in the 

medium/high variant, and therefore more diagnostic of the lower floodplain include, 

Toxicodendron radicans (climbing poison ivy), Carpinus caroliniana var. virginiana 

(musclewood), and Cornus amomum (silky dogwood). 

Characteristic herbs include Coptis trifolia var. groenlandica (goldthread), Trillium 

undulatum (painted trillium), Thelypteris simulata (Massachusetts fern), Maianthemum 

canadense (Canada mayflower), and other common forest herbs. On drier floodplains, 

species of dry to dry-mesic sites are abundant, including Pteridium aquilinum (bracken 

fern), Carex pensylvanica (Pennsylvania sedge), Oryzopsis asperifolia (mountain rice), 

Mitchella repens (partridge-berry), Aralia nudicaulis (wild sarsaparilla), and Trientalis 

borealis (starflower). 

Most higher floodplain forests are set farther back from the river channel than the 

lower floodplain forest. In other locations, higher floodplains occur along natural levees 

and other areas adjacent to the main channel, and low floodplains are found farther from 

the main channel. In many areas, high and low floodplain forests form complex mosaics 

with other floodplain communities. 

DISTRIBUTION: Throughout New Hampshire along major streams and minor rivers, and on some 

terraces of major rivers above low floodplain forests. 

COMMENTS: In two examples, Nyssa sylvatica (black gum) cover is significant in the tree 

canopy and understory layers. More information is needed on the distribution and significance 

of black gum in floodplain settings. 


GOOD EXAMPLES: Lamprey River (Epping and Lee); Bellamy River and Blackwater Brook 

(Dover); Baboosuc Brook (Merrimack); Pointer Club Brook (Bedford/Merrimack); Cohos Brook 

(Manchester); Soucook River (Concord). 

SOURCES: NH Heritage field surveys; Sperduto and Crow (1994); Nichols and Sperduto (1997). 

• Balsam fir floodplain forest (S2) 

Abies balsamea-Acer rubrum/Carex stricta floodplain forest 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This is a woodland or forest floodplain 

community type found in northern and occasionally central New Hampshire. It occurs along 

major rivers in the mountains and along minor rivers and major streams (third- and fourth-order) 

in other settings with local cold-climate conditions. Abies balsamea (balsam fir), other northern 

species, and species indicative of low to moderate soil nutrient availability are common. Species 

indicative of high soil nutrient availability are absent. Woodland examples often have dense 

shrub and herbaceous layers. 

SOILS/GEOLOGY/HYDROLOGY: Soils are fine sandy loams or loams that occur in valley bottoms 

of montane rivers or other settings with frigid soils or pronounced cold-air drainage (Natural 

Resources Conservation Service frigid temperature regime). Flashy montane rivers are 

associated with several examples of this floodplain type and may be indicative of a more 

temporary or infrequent flooded regime compared to other floodplain forest community types. 

Examples occur from 150 m (500 ft.) to more than 370 m (1200 ft.) elevation. 

CHARACTERISTIC VEGETATION: Abies balsamea (balsam fir) is indicative of this type, and is 

usually abundant or co-dominant in the canopy or subcanopy along with Acer rubrum (red 

maple). Prunus serotina (black cherry) and Pinus strobus (white pine) are frequent and 

occasionally abundant, and Acer saccharinum (silver maple) is occasional. Tsuga canadensis 

(hemlock) and Picea rubens (red spruce) are infrequent. Species found in other floodplain forest 

types but more frequent or abundant in this type include Calamagrostis canadensis (blue-joint), 

Carex stricta var. strictior (tussock sedge), Spiraea alba (meadow-sweet), Brachyelytrum 

erectum var. glabratum (northern short husk grass), Carex novae-angliae (New England sedge), 

Corylus cornuta (beaked hazel-nut), and Carex intumescens (inflated sedge). Tussock sedge is 

the nearly constant and usually present only in its rhizomatous form (non tussock-forming). 

Northern or boreal plants are frequent as a group and include Coptis trifolia var. groenlandica 

(goldthread), Cornus canadensis (bunchberry), Aster acuminatus (whorled aster), and New 

England sedge. 

Species characteristic of this and other floodplain forest communities include Onoclea 

sensibilis (sensitive fern), Thalictrum pubescens (tall meadow-rue), Viburnum nudum var. 

cassinoides (witherod), Viburnum dentatum var. lucidum (northern arrow-wood), Solidago 

rugosa (rough goldenrod), Osmunda regalis var. spectabilis (royal fern), Alnus incana var. 

americana (speckled alder), and Uvularia sessilifolia (sessile-leaved bellwort). 


DISTRIBUTION: Mountain rivers of northern New Hampshire and occasionally central New 

Hampshire. 

COMMENTS: Some examples contain a mixture of red and silver maple and are transitional to 

silver maple types. These usually occur at sites with one of the silver maple community types at 

lower floodplain elevations. 

GOOD EXAMPLES: Magalloway River (Errol); Swift River (Albany); Pine River (Ossipee); Big 

River (Barnstead). 


• Sycamore floodplain forest (S1) 

Platanus occidentalis floodplain forest 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: Sycamore floodplain forests in New Hampshire 

are known only from low floodplains of the Ashuelot River north of Surry Mountain Lake and 

the North River in Lee. Platanus occidentalis (sycamore) reaches the northern limit of its range 

in the northeast in southern New Hampshire and southwestern Maine. This type of forested 

floodplain appears to be regionally uncommon to rare. The Ashuelot River site, the only 

example to be sampled in New Hampshire, has a relatively high plant species richness compared 

to other floodplain forest community types. 

SOILS/GEOLOGY/HYDROLOGY: The sycamore floodplain forest site along the Ashuelot River is 

generally restricted to floodplain islands and the bases of steep slopes. In this stretch of the 

Ashuelot River, the channel substrate is largely cobble and flood events appear to be “flashy” in 

nature. Soils are sandy loam, sand, or gravelly sand. The pH measured from one soil profile was 

5.3. 

CHARACTERISTIC VEGETATION: This community is characterized by a sparse to moderately well 

developed canopy dominated by Platanus occidentalis (sycamore) with a tall, well developed 

Carpinus caroliniana var. virginiana (musclewood) shrub layer. Tree canopy associates include 

Acer rubrum (red maple), Acer saccharum (sugar maple), Ulmus americana (American elm), 

Carya cordiformis (bitternut hickory), and less frequently Juglans cinerea (butternut). Closer to 

the lake where flooding is more frequent, the woody shrub and sapling layer is often absent. In 

these areas, there is a tall, dense herbaceous layer dominated by Polygonum virginianum 

(jumpseed), Matteuccia struthiopteris var. pensylvanica (ostrich fern), and Calamagrostis 

canadensis (blue-joint). The sycamore floodplain forest is one of several community types that 

form a community mosaic at the site. Associated floodplain communities include shrub thickets, 

emergent marsh, riverside sand and gravel barrens, and other types of forested floodplains. In 

certain areas, a sugar maple floodplain forest occurs on medium to high floodplain elevations 

adjacent to the sycamore floodplain forest. 

DISTRIBUTION: Presently known only to occur along the Ashuelot River (Surry) and the North 

River (Lee). 


COMMENTS: Although not well sampled, this is a reasonably distinct association. Additional 

sampling and research will help determine its distribution and regional significance. 

GOOD EXAMPLES: Ashuelot River (Surry). 


FORESTS ON ACIDIC SOILS 

• Low hemlock-hardwood/cinnamon fern forest (S4) 

Tsuga-Acer rubrum-Betula alleghaniensis/Osmunda cinnamomea forest 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This community occurs in imperfectly to 

somewhat poorly drained areas along stream drainages, high floodplains, inactive river terraces, 

and other upland-wetland ecotones. It is characterized by Tsuga canadensis (hemlock), Acer 

rubrum (red maple), and a mixture of other wetland and upland plant species. Examples may 

occur along a narrow transition zone between uplands and wetlands or may be broader in nature 

and cover several acres. 

Hemlock is an important component in many other types of forest communities, but only 

reaches overstory dominance or codominance in hemlock forests on upland sites and in this 

community along upland-wetland ecotones. Sites where hemlock is abundant are characterized 

by open, dark understories. Although hemlock may be present in the understory in low density, 

it appears to maintain itself by out-competing other suppressed tree species for light and nutrients 

(Rogers 1978). Hemlock saplings may persist for decades or even centuries in the understory 

and still respond well to canopy openings. Maximum hemlock ages in the region exceed 500 

years. The centers of most older trees are rotten, preventing accurate aging of individual trees. 

Deer often winter in these areas where snow cover is light and movement is therefore easier. 

SOILS/GEOLOGY/HYDROLOGY: Soils vary from loamy sands to sandy loam till and river/kame 

terrace soils with a shallow water table (within 0.3 m (1 ft.) of soil surface for portion of growing 

season), and are nutrient poor (oligotrophic to submesotrophic). Mottles are evident within 30 

cm (12 in.) of the soil surface in some examples, while others have deep A horizons (tending to 

obscure mottles) over moist to wet sediments. Although some sub-surface seepage may 

influence certain examples, this community appears distinct from seepage forest and forest seep 

communities, which tend to have relatively constant surface or near-surface seepage influence. 

Soils include series Au Gres, among other types. 

CHARACTERISTIC VEGETATION: Tsuga canadensis (hemlock) and Acer rubrum (red maple) 

dominate in the overstory. Canopy associates may include Pinus strobus (white pine), Betula 

alleghaniensis (yellow birch), and less frequently Quercus bicolor (swamp white oak), Quercus 

rubra (red oak), Betula lenta (black birch), Ulmus americana (American elm), and Prunus 

serotina (black cherry). At upland-wetland ecotones in other landscape positions, Fraxinus 

americana (white ash) may also be prominent in the tree canopy. Other woody species can 

include Kalmia angustifolia (sheep laurel), Vaccinium corymbosum (highbush blueberry), 


Viburnum nudum var. cassinoides (witherod), Fagus grandifolia (American beech), Rosa 

palustris (swamp rose), Rubus occidentalis (western black raspberry), Sambucus canadensis 

(common elderberry), Acer pensylvanicum (striped maple), Viburnum alnifolium (hobblebush), 

Picea rubens (red spruce), and Abies balsamea (balsam fir). 

Although the overstory association can approximate certain upland forests, more mesic to 

wet conditions are indicated by the presence of Osmunda cinnamomea (cinnamon fern), 

Osmunda claytoniana (interrupted fern), Arisaema triphyllum (Jack-in-the-pulpit), Thelypteris 

palustris (marsh fern), Lonicera canadensis (Canada honeysuckle), Lindera benzoin (spicebush), 

and various mosses. Other herbs may include Thelypteris noveboracensis (New York fern), 

Aralia nudicaulis (wild sarsaparilla), Aster acuminatus (whorled aster), Dryopteris intermedia 

(intermediate wood fern), Mitchella repens (partridge berry), Oxalis acetosella (wood sorrel), 

and Clintonia borealis (blue-bead lily). 

DISTRIBUTION: Throughout most of New Hampshire south of and including the White 

Mountains on valley bottoms and drainages of upland till and river/kame terrace soils. 

COMMENTS: Although not well-sampled, this is a reasonably widespread and apparently distinct 

association, but the transition to related upland and wetland communities may be indistinct on 

the ground. Additional sampling would substantiate or clarify its distinctiveness. 

GOOD EXAMPLES: East of swamp north of Birch Hill, Allard Brook, and east of White Ledge 

(Albany); Johnson Creek (Durham). 

SOURCES: NH Heritage field surveys; Nichols and Sperduto (1997). 


VERNAL POOLS 

• Vernal woodland pool (S3) 

This community occurs as small, vernally flooded woodland pools that draw down 

completely or nearly completely over the course of the summer. Typically, vernal pools are 

small (less than 0.1 acres) and are sparsely or unvegetated. Larger isolated vernal basins with 

perennial or annual vegetation are alternatively referred to as basin marshes, although they are 

functionally still “vernal pools.” Vernal pools are important feeding and breeding ground for 

reptiles, amphibians, and invertebrates; Identification and Documentation of Vernal Pools 

(Tappan 1997) has additional information on vernal pools and their values. A Vernal Pool 

Committee is coordinated by the NH Fish & Game Department’s Nongame & Endangered 

Wildlife Program. More data are needed on all vernal wetlands. 

• Vernal floodplain pool (S2) 

Many of the low swales occupied by oxbow marshes are technically "vernal pools" in that 

the water level draws down completely over the course of the season and the pools are used by 

numerous amphibians and reptiles for feeding, hibernation, and/or as temporary flood refugia 

(Carroll 1994). When these swales are larger than can be shaded by the tree canopy, the 

vegetation becomes strongly influenced by open light conditions and are consequently 

distinguished from their smaller counterparts discussed here (see also emergent marsh and 

oxbow marsh discussion). Smaller vernal pools (generally smaller than a tree canopy) occur 

throughout the floodplain forests of many New Hampshire rivers. Such vernal wetlands are 

forested vernal pools and exhibit different, albeit variable, vegetation characteristics. They often 

lack the robust marsh vegetation found in larger oxbow marshes and are largely shaded from 

long periods of sunlight. There may also be flood-length differences. It is uncertain what 

functional differences these two types generate for fauna. 

These small isolated basins are presumably formed by local eddy swirls or some other flow 

and deposition phenomena of the dynamic floodplain. The age of these vernal pools is uncertain. 

Regardless, they are hydrologically and ecologically different than most vernal pools on till or 

outwash due flooding by moving water and the possible temporary exposure to predation by fish 

during high water. 

Forested floodplain vernal pools observed on the Lamprey River exhibited a wide range of 

morphologies ranging from shallow to deep, small to large, and in different positions and 

distances relative to the river channel and water table (Sperduto and Crow 1994). Vegetation is 

often sparse when present and quite variable from one basin to the next. These ecological and 

vegetative differences and seasonal changes may also influence seasonal faunal use patterns. 


ESTUARINE SYSTEMS 

Estuarine communities in New Hampshire occur in subtidal and intertidal coastal habitats 

connected to the ocean but semi-enclosed by land and protected from high energy wave action. 

Access to the ocean is open, partly obstructed, or sporadic. Subtidal habitats are influenced by 

the tides but continuously submerged while intertidal habitats are exposed and flooded by the 

tides (including spring tide and splash zone areas). Ocean water within the estuarine system is at 

least occasionally diluted by freshwater runoff. In certain areas, evaporation may increase 

salinity above that of the open ocean. The estuarine system extends seaward to an imaginary line 

drawn across the mouth of a bay or river or to the seaward limit of wetland vascular plants when 

they are not included within the imaginary line, and upstream and landward to where oceanderived 

salts are less than or equal to 0.5 parts per thousand during the period of average annual 

low freshwater flow (Cowardin et al. 1979). 

Subtidal communities include the Saline/Brackish Subtidal Channel/Bay Bottom and its 

variants. Intertidal communities can be broken into 3 broad groups according to flooding 

frequency: (1) upper intertidal – the irregularly flooded zone (substrate flooded less than daily) 

occurring between the upper reaches of the spring tide/splash zone and mean high tide including 

wetlands beyond the upper reach of spring tides but periodically infused with salt water during 

storm events (supporting coastal salt pond marsh, high salt marsh, brackish marsh, high brackish 

tidal river-bank marsh, and coastal shoreline strand/swale); (2) middle intertidal – the regularly 

flooded zone (substrate flooded at least once daily) occurring between the mean high tide and 

mean low tide (supporting low salt marsh, low brackish tidal river-bank marsh, saline/brackish 

intertidal flat, and intertidal rocky shore); and (3) lower intertidal – the irregularly exposed zone 

(substrate exposed less than daily) occurring between the mean low tide and very low spring tide 

(supporting the lower reaches of the saline/brackish intertidal flat and intertidal rocky shore). 

INTERTIDAL MARSHES 

• Low salt marsh (S3) 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: Spartina alterniflora (smooth cord-grass) 

dominates the low salt marsh, an intertidal zone occurring between mean sea level and mean 

high tide. The low salt marsh is one of several tidal and subtidal communities that occur in 

habitats protected from high-energy wave action in the estuarine ecosystem. They have formed 

together with high salt marshes, along the coast behind rocky spits, barrier beaches, and sand 

bars or along bays and rivers. Low salt marshes grade into intertidal flats and subtidal 

communities seaward and high salt marsh landward. A band of smooth cord-grass, reaching 

heights of ca. 1-2 m (ca. 4-6 ft.), is often restricted to a narrow fringe along ditches, creeks, 

rivers, and bays. Where slopes are more gentle, smooth cord-grass may cover broader areas. 

The ratio of high marsh to low marsh in New Hampshire is 14:1 (Spinner 1969). Salt marshes 

are the largest natural grassland ecosystems in New England. 


Salt marsh pannes and pools, low areas isolated from tidal creeks, occur in both the high and 

low marsh. Species composition varies with salinity, hardness of substrate, elevation, soil 

oxygen, hydroperiod (duration and frequency of tidal flooding), and other factors. Low marsh 

pannes and pools are regularly flooded and often unvegetated with a soft, silty mud substrate. 

Irregularly flooded high marsh pannes and pools vary in species composition, with the highest 

species richness and cover generally found in the shallow and relatively dry forb pannes. 

Salinity fluctuates in response to tidal flooding, evaporation, and rainfall. 

The low marsh has more frequent tidal flooding, lower soil oxygen, and reduced soil salinity 

compared to the high marsh. Refer to the high salt marsh description for additional information 

on salt marsh ecology, biology, and land use history. 

SOILS/GEOLOGY/HYDROLOGY: The following soil description is based on a detailed survey of 

New Hampshire tidal marsh soils prepared by Breeding, Richardson, and Pilgrim (1974): 

Coastal low marsh soils and some low marsh soils around the Great Bay complex are organic 

materials 16 to 50" thick overlying sandy materials (Terric Sulfihemists over sand). Much of the 

high and low marsh soil along stream and river mouths entering Great Bay and the narrow 

margins around the bay are organic materials 16 to 50" thick overlying silty materials (Terric 

Sulfihemists over silt). 

The establishment of Spartina alterniflora (smooth cord-grass) in the intertidal low marsh 

and the tangle of brown algae around the grass base help trap coarse sediments brought in by the 

tides. A large percentage of smooth cord-grass culms, sheered off during the winter near their 

base by ice and wave action, are carried away by tidal currents and not incorporated into the 

intertidal peat. As a result of these processes, the intertidal peat is coarser in structure and with a 

lower volume of organic matter compared with high marsh peat. 

Surface water salinity fluctuates widely according to seasonal variation in freshwater 

discharge, with greater variation occurring within the Great Bay complex than in estuaries closer 

to the coast (Short 1992). There is also a pattern of decreased surface water salinity from coastal 

marshes to marshes occurring in Great Bay and its tributaries. Salinity in the Great Bay complex 

is generally greater than 20 parts per thousand (ppt) except during major spring runoff events, 

whereas coastal marshes remain closer to 30 ppt year-round (Short 1992). Salt marsh soil water 

salinity roughly corresponds to polyhaline levels (18–30 ppt). Salinity levels less than 18 ppt but 

greater than 0.5 ppt (meso- and oligohaline levels) typically support brackish marsh 

communities. Freshwater emergent marshes occur where salinity levels are 0.5 ppt or less during 

the period of annual low freshwater flow. 

CHARACTERISTIC VEGETATION: Spartina alterniflora (smooth cord-grass) dominates the 

physically stressful low marsh largely due to limited competition and its ability to tolerate polyto 

euhaline soil water salinity and oxygenate its roots and rhizosphere. Associated vascular 

halophytes in low abundance may include Salicornia europaea (common glasswort), Atriplex 

hastata (halberd-leaved orach), Atriplex glabriuscula (smooth orache), Eleocharis parvula 

(small spike-rush)*, Suaeda spp. (sea blites), Spergularia marina (salt-marsh sand-spurrey), and 


macroalgae (seaweed) such as Ascophyllum nodosum and Fucus spp. (rockweeds). As salinity 

decreases, Scirpus robustus (stout bulrush) and Typha angustifolia (narrow-leaved cat-tail) 

become more prominent and may dominate the low marsh in brackish environments (see low 

brackish tidal river-bank marsh description). 

DISTRIBUTION: Restricted to sheltered areas of the seacoast in the Coastal Lowland subsection. 

COMMENTS: This is a distinct, narrowly defined natural community, most similar to the low 

brackish tidal river-bank marsh described elsewhere. 

GOOD EXAMPLES: Blackwater and Hampton River Salt Marsh (Seabrook, Hampton Falls, 

Hampton). 

SOURCES: NH Heritage field surveys; Breeding, Richardson, and Pilgrim (1974); Redfield 

(1972). Prepared by Bill Nichols. 

• High salt marsh (S3) 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: The high salt marsh is one of several tidal and 

subtidal communities occurring in habitats protected from high-energy wave action in the 

estuarine ecosystem. They have formed, together with low salt marshes, along the coast behind 

rocky spits, barrier beaches, and sand bars or along bays and rivers. High salt marsh grades into 

low salt marsh, intertidal flats, and subtidal communities seaward and depending on local 

conditions, brackish marsh, fresh water wetlands, or upland communities landward. A salt shrub 

community dominated by Iva frutescens ssp. oraria (marsh elder)* is well developed along the 

coast south of New Hampshire where it forms the ecotone between the high salt marsh and 

upland communities but it is poorly developed and rarely present along the landward edge of the 

state’s 6,200 acres of salt marsh. Salt marshes are the largest natural grassland ecosystems in 

New England. 

Along the east coast of North America, three types of coastal salt marsh have been described: 

(1) a “Fundy Type” to the north of New England, (2) a “Coastal Plain Type” south of New 

Jersey, and (3) a “New England Type” from Maine to New Jersey (Johnson 1925). The 

distinction between the types is based on development history and organic content of the marsh 

peat. The Fundy Type is characterized by a primarily mineral, compact, reddish silt soil eroded 

by the great tidal ranges from relatively soft bedrock. The Coastal Plain Type is underlain by 

gray silt eroded from soft bedrock. Rivers deposit the gray silt in large quantities near their 

mouth forming broad, relatively flat marshes in estuaries or sounds. Marsh soils in the New 

England Type are primarily fibrous marine peat with little silt supplied by hard, weather resistant 

bedrock. New England Type salt marshes comprise less than 2% of the marsh along the east 

coast of the United States (Reimold 1977) and are estimated to be 4,000 years old. The rate of 

sea level rise slowed sufficiently during this period to allow for the establishment and growth of 

salt marshes (Redfield 1972). Salt marshes replaced brackish marshes and uplands landward and 

accreting intertidal flats seaward. 


The transition between high and low salt marsh occurs approximately at the mean high water 

mark; high salt marsh stretches landward from mean high water to the upper reaches of spring 

tides. The high salt marsh, usually dominated by the perennial grass Spartina patens (saltmeadow 

cord-grass), covers more area than the low salt marsh. The low salt marsh typically 

consists of a narrow fringe of Spartina alterniflora (smooth cord-grass) along ditches, creeks, 

rivers, and bays. Where slopes are more gentle, smooth cord-grass dominated low marsh may 

cover broader areas. The ratio of high marsh to low marsh in New Hampshire is 14:1 (Spinner 

1969). Although the water table is always at or near the surface in the high marsh, tidal flooding 

decreases landward with increased elevation and microtopography, creating areas with higher 

soil oxygen that support a variety of species. 

Marsh plant zonation results from several factors including ice-scouring, land use history, 

storms, hydroperiod (duration and frequency of tidal flooding), elevation of substrate, nutrient 

availability, salinity, soil oxygen, and concentration of growth inhibitors in the sulfihemist soils 

(Breeding et al. 1974; Howes et al. 1986) and from competitive interaction and biological 

facilitation (Bertness 1992). Many of these factors and processes are interrelated, but vary along 

gradients at different rates or quantities (Zoltai and Vitt 1995). Smooth cord-grass dominates the 

physically stressful low marsh due to its ability to oxygenate its roots and rhizosphere. Saltmeadow 

cord-grass, sensitive to tidal flooding, competitively excludes smooth cord-grass from 

the high marsh. Along the upland edge of the marsh, salt-meadow cord-grass is itself 

competitively excluded by Juncus gerardii (salt marsh rush), the marsh perennial most 

susceptible to tidal flooding (Bertness 1990). At Hampton Harbor, the mean tidal range is 8.3 ft. 

with spring tides averaging 9.5 ft. Here, the high marsh rises from approximately 4 ft. above 

mean sea level at its lower end to 5 ft. above mean sea level at the landward limit of the salt 

marsh rush zone. Salt marsh vegetation is very dynamic and traditional successional concepts 

have limited application in addressing patterns of vegetation change (Niering and Warren 1980), 

largely due to ongoing sea level rise. 

Since the first European settlers arrived on the coast until recently, pannes were routinely 

drained by farmers to increase the productivity of salt-meadow cord-grass and Distichlis spicata 

(spike-grass) for hay, pasturage, and mulch. New Hampshire’s salt marshes were also ditched in 

an effort to reduce salt marsh mosquito (Aedes sollicitans) populations by draining water in their 

breeding pannes into tidal creeks. The environmental impact of ditching can include shifted 

species composition across the marsh to high marsh plants more characteristic of drier 

conditions, a reduction in insect, mollusk, and crustacean populations, a reduced flooding 

duration and lowered water table (Bourn and Cottam 1950; Britton et al. 1915), a decline in 

shorebirds and waterfowl (Bradbury 1938), and loss of submerged aquatics including Ruppia 

maritima (widgeon-grass), and the state-threatened Potamogeton pectinatus (sago pondweed)* 

and Zannichellia palustris (horned pondweed)*. Spoil deposits from the ditches may support 

high marsh grasses and Iva frutescens ssp. oraria (marsh elder)*, a state-threatened shrub (Miller 

and Egler 1950). 


Ditching can also cause wetter conditions on the marsh when: (1) ditches cut through creek 

levees and provide a pathway for tidal water onto the high marsh (Warren and Niering 1993); (2) 

slumping spoil blocks the ditch causing water to pond (Miller and Egler 1950); (3) ditches 

interrupt the course of a small creek and ponding occurs in the isolated, abandoned portion of the 

creek (Redfield 1972); and (4) mini-levees develop along the ditch margins trapping water (Shea 

et al. 1975). 

Twenty percent, or 1240 acres of New Hampshire’s salt marshes have been degraded by 

varying degrees of non-natural restrictions to tidal flow (Soil Conservation Service 1994). 

Where restrictions are severe, salt marshes are replaced by brackish or fresh water wetlands. 

Other causes of salt marsh deterioration from human activity include filling, draining, increased 

nutrient inputs, increased and, in some cases, decreased sediment inputs, introduction of invasive 

plant species, and excess freshwater runoff (Soil Conservation Service 1994). 

SOILS/GEOLOGY/HYDROLOGY: The following soil description is based on a detailed survey of 

New Hampshire tidal marsh soils prepared by Breeding, Richardson, and Pilgrim (1974): High 

marsh soils of the coastal marshes and those bordering the smaller streams flowing into Great 

and Little Bays are generally organic materials thicker than 50" over sand, silt, or bedrock (Typic 

Sulfihemists). Lesser amounts of Sulfaquents over sand underlie high marsh at the extreme 

seaward edge of coastal margins, small areas on the Great Bay’s western side, and along some 

streams flowing into the bay. Much of the high and low marsh soil along stream and river 

mouths entering the Great Bay complex and the narrow margins around the bay are organic 

materials 16 to 50" thick overlying silty materials (Terric Sulfihemists over silt). 

A large percentage of vegetative matter on the high marsh is incorporated into the high marsh 

peat and not removed by winter ice scour as occurs in the low marsh. In addition, fine sediments 

are deposited on the upper surface of the peat during spring tide flooding. As a result, high 

marsh peat has finer sediments and a greater volume of organic matter compared with low marsh 

peat. 


discharge with greater variation occurring within the Great Bay complex than in estuaries closer 


marshes to marshes occurring in Great Bay and its tributaries. Salinity in the Great Bay complex 

are generally greater than 20 parts per thousand (ppt) other than during major spring runoff 

events, whereas coastal marshes remain closer to 30 ppt year-round (Short 1992). Salt marsh 

soil water salinity roughly corresponds to polyhaline levels (18–30 ppt). Salinity levels less than 

18 ppt but greater than 0.5 ppt (meso- and oligohaline levels) typically support brackish marsh 

communities. Freshwater emergent marshes occur where salinity levels are 0.5 ppt or less during 

the period of annual low freshwater flow. 

CHARACTERISTIC VEGETATION: In addition to Spartina patens (salt-meadow cord-grass), other 

common plants on the high marsh include Spartina alterniflora (smooth cord-grass; short form), 

Distichlis spicata (spike-grass), and Juncus gerardii (salt marsh rush). The short form morphology 


of smooth cord-grass is attributed to poorer drainage, less oxidized sediments, decreased nutrient 

availability, and higher concentrations of sulfides and other plant growth inhibitors often occurring 

just above mean high water where the marsh becomes flat (Howes et al. 1986). Spike-grass often 

forms pure stands in wetter, more poorly drained areas, or mixes with salt-meadow cord-grass, 

growing at similar elevations on the high marsh. Salt marsh rush often dominates landward of saltmeadow 

cord-grass in narrow vegetative zones with decreased tidal flooding and soil water 

salinity, beginning at about mean spring high water. Only the spring tides and storm surges reach 

this area along the upper edge of the high salt marsh. This zone has the highest species richness 

within the high marsh and includes Solidago sempervirens (seaside goldenrod), Panicum virgatum 

(switch-grass), Hierochloe odorata (sweet grass), Carex hormathodes (necklace sedge), Festuca 

rubra (red fescue), Aster novi-belgii (New York aster), Elymus virginicus (Virginia wild rye), 

Teucrium canadensis (germander), Sanguisorba canadensis (Canadian burnet), Elytrigia repens 

(quack-grass), Spartina pectinata (fresh-water cord-grass), Ligusticum scothicum (Scotch lovage), 

and Juncus arcticus var. littoralis (shore rush). Less frequent high marsh species are Polygonum 

ramosissimum (bushy knotweed), P. exsertum (exerted knotweed)*, P. prolificum (prolific 

knotweed)*, Potentilla anserina (silverweed), Aster tenuifolius (large salt marsh aster)*, and Aster 

subulatus (annual salt marsh aster). 

The salt shrub community, common in southern New England, rarely occurs landward of the 

high salt marsh in New Hampshire. Small, poorly developed shrubland pockets are 

characterized by the state-threatened shrub Iva frutescens ssp. oraria (marsh elder)* and the high 

marsh herbs switch-grass, salt marsh rush, salt-meadow cord-grass, New York aster, and seaside 

goldenrod. This plant association is also found on elevated areas across the high marsh (ditch 

ridges and ice-berm mounds). Because this community is poorly developed in New Hampshire, 

it is probably best treated as a plant association within the high salt marsh. 

Plants often found on low natural levees include Suaeda spp. (sea-blites), Puccinellia 

maritima (seaside alkali-grass), and Atriplex hastata (halberd-leaved orach). Along larger marsh 

creeks, levees several meters wide typically rise 5–15 cm (2–6") (Nixon 1982). Areas along the 

upper edge of the high salt marsh influenced by freshwater streams, ephemeral channeled runoff, 

or groundwater discharge often support brackish marsh communities. 

Salt marsh pannes, pools, and ditches – low areas isolated from tidal creeks – occur in both 

the high and low marsh. Salt marsh pannes and pools form distinct associations that could 

alternatively be treated as small-scale but distinct natural communities. Because of their smallscale 

and dependence on larger-scale salt marshes for their existence, pannes and pools are 

treated as part of the salt marsh community. 

Species composition varies with salinity, hardness of substrate, elevation, soil oxygen, 

hydroperiod, and other factors. Low marsh pannes and pools are regularly flooded and often 

unvegetated with a soft, silty mud substrate. Irregularly flooded high marsh pannes and pools 

vary in composition, with the highest species richness and cover generally found in the shallow 

and relatively dry forb pannes. Salinity fluctuates in response to tidal flooding, evaporation, and 

rainfall. 


Shallow pannes are created by damage to Spartina patens (salt-meadow cord-grass) and 

other high marsh vegetation from ice erosion or smothering by stranded mats of Spartina 

alterniflora (smooth cord-grass) (Bertness 1992) and other flood-deposited plant litter or trash. 

Redfield (1972) outlines five processes accounting for the formation of “pond holes” or deep 

pools: (1) relics of intertidal pannes formed in the transition from slough marsh to high marsh; 

(2) slumping banks blocking tidal creeks causing water to pond, followed by pool enlargement 

by turf decomposition; (3) decay of surface turf from inadequate drainage forming rotten spots; 

(4) local failure of marsh development; and (5) the isolated portion of an abandoned minor creek 

created when ditches dug for mosquito control interrupt the creeks course. Deep pools are also 

created when Open Marsh Water Management personnel deepen existing fish refuges to 0.9 m (3 

ft.) deep or more to increase the survival rate of “marsh minnows” (predators of mosquito larvae) 

during dry periods. The disappearance of pond holes from older sections of salt marsh suggest 

they may be a temporary part of the marsh ecosystem (Chapman 1960). Breeding et al. (1974) 

note the formation of “quacking mats” from smooth cord-grass growth and consolidation across 

the surface of pond holes at Sagamore Creek Marsh in Portsmouth, NH. 

High marsh panne salinity levels are typically in the range of 40–50(-60) ppt. Under the 

most extreme conditions (e.g., high salinity or low oxygen) pannes may be devoid of vegetation. 

Purple sulfur-bacteria thrive in deeper pannes on the high salt marsh. Several panne types can be 

distinguished, all ranging in size from less than 1 m 2 to over 100 m 2 : 

1. Triglochin (forb) panne: Very shallow, briefly flooded, moderately vegetated forb 

pannes are typically dominated by Triglochin maritimum (arrow grass). Other common 

species include Distichlis spicata (spike-grass), Juncus gerardii (salt marsh rush), 

Spartina patens (salt-meadow cord-grass), and Spartina alterniflora (smooth cord-grass; 

short form). Less frequent species are Plantago maritima (salt marsh plantain), 

Limonium carolinianum (sea lavender), Atriplex hastata (halberd-leaved orach), Glaux 

maritima (sea milkwort), Puccinellia maritima (seaside alkali-grass), and Potentilla 

anserina (silver-weed). Lower portions of the panne where evaporation and poor 

drainage create high salinity levels may remain unvegetated or support the succulent 

Salicornia europaea (common glasswort). Common glasswort may also colonize 

recently exposed peat in shallow, hypersaline depressions, often followed by spike-grass, 

which shades the soil, reducing evaporation and soil salinity. Spike-grass is then 

replaced by the more competitive and turf-forming salt-meadow cord-grass or salt marsh 

rush (Bertness 1992; Brown 1993). An inverse relationship exists between salt tolerance 

and competitive ability in New England’s high marsh plants with the most competitive 

species being most successful in lower salt environments (Bertness 1992). 

Forb pannes also provide habitat for the state-threatened Agalinis maritima (seaside 

gerardia)*, Salicornia bigelovii (Bigelow’s glasswort)*, and the state-endangered 

Puccinellia paupercula var. alaskana (Alaskan goose-grass)*. Pluchea odorata (marshfleabane)*, 

a state-endangered species, may be found in this habitat and in brackish 

marsh communities. 


2. Spartina alterniflora (short form) panne: Shallow anaerobic depressions with poor 

drainage, low nutrient availability, and high concentrations of sulfides and other plant 

growth inhibitors promote the growth of the short form (6–12" tall) of Spartina 

alterniflora (smooth cord-grass) (Howes et al. 1986). Spartina alterniflora pannes occur 

on less firm peat soils and appear to be somewhat deeper, often larger, and saturated or 

flooded for longer periods than forb pannes. However, as soil saturation and ponding 

increase, the abundance of smooth cord-grass usually decreases (Redfield 1972). Species 

occurring in low abundance include Salicornia europaea (common glasswort), Atriplex 

hastata (halberd-leaved orach), and few other vascular halophytes. This panne type is 

most often found on the high salt marsh but can occasionally occur on the upper margins 

of the low salt marsh. Wetter areas dominated by the short form of smooth cord-grass are 

occasionally formed from mini-levees trapping water along ditch margins (Shea et al. 

1975). 

3. Salt marsh mosquito panne: Sparsely-vegetated salt marsh mosquito pannes are most 

often found on the upper half of the high salt marsh. They are generally deeper than both 

forb and Spartina alterniflora pannes and are typically flooded by the higher of the two 

spring tides (new or full moon tide), drying-out two to three weeks later. Because they 

are not permanently flooded, “marsh minnows” (stickleback (Pungitius pungitius, 

Gasterosteus aculeatus, and Apeltes quadracus) and mummichog (Fundulus 

heteroclitus)), predators of salt marsh mosquitoes (Aedes sollicitans) and other 

invertebrates, are absent or in low numbers. The flooding duration generally restricts 

emergent halophytic graminoids and forbs to the shallower panne margin while 

preventing the growth of Ruppia maritima (widgeon-grass), a species typically found in 

semi-permanently to permanently flooded pannes, pools, and ditches. 

When the panne is dry, female salt marsh mosquitoes lay eggs on the exposed 

surface. After the panne is flooded by the new or full moon tide, the salt marsh mosquito 

larvae develop through several instars and emerge as adults (5-)7–10 days later. Other 

mosquito species may also successfully breed in these pannes during the warmer months, 

particularly when salinity levels are reduced during periods of significant rainfall. 

4. Ruppia/marsh minnow deepwater panne/pool/ditch: Semi-permanently and 

permanently flooded areas characterized by Ruppia maritima (widgeon-grass) are 

common on the high salt marsh. Deepwater pannes, pools, and ditches provide habitat 

for “marsh minnows” (stickleback (Pungitius pungitius, Gasterosteus aculeatus, and 

Apeltes quadracus) and mummichog (Fundulus heteroclitus)), and are important foraging 

areas for many species of shorebirds. 

Emergent halophytic graminoids and forbs are generally restricted to shallow 

margins, the principal habitat for Scirpus maritimus (salt marsh bulrush). The margin 

may also be steep and deep, without emergent marsh vegetation. Purple sulfur-bacteria is 

often common across the stagnant water surface of deeper pannes and pools. The statethreatened 

Potamogeton pectinatus (sago pondweed)* and Zannichellia palustris (horned 


pondweed)* are submerged aquatics that may be found in this habitat. Deepwater pannes 

and pools occasionally occur on the upper margins of the low salt marsh. 

• Brackish marsh (S2S3) 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: Brackish marshes occasionally occur along the 

upper margins of high salt marshes and high brackish tidal river-bank marshes where sufficient 

fresh water runoff or groundwater discharge flows onto the marsh surface. They are tidally 

flooded by salt water only during spring tides and storm surges. This hydrologic regime supports 

brackish marsh species and other species most often found in fresh or salt marshes but tolerant of 

brackish conditions and able to successfully compete in this environment. The high and low 

brackish tidal river-bank marsh are two similar communities but are tidally flooded more 

frequently than by spring tides alone. As the sea level continues to rise (1–2 mm/year), brackish 

marsh may be submerged and replaced by salt marsh, while new areas suitable for brackish 

marsh may form landward. 

SOILS/GEOLOGY/HYDROLOGY: Sulfihemist soils with low surface salt content likely underlie 

most brackish marsh communities. However, Sulfihemist soils supporting brackish marshes are 

typically too small to be readily mapped at the scale used in the New Hampshire soil survey 

(Breeding et al. 1974). 

Soil water salinity generally ranges from greater than 0.5 parts per thousand (ppt) to less than 

18 ppt (oligo- to mesohaline). Salinity levels greater than or equal to 18 ppt (poly- to euhaline) 

typically support salt marsh. Freshwater emergent marshes occur where salinity levels are 0.5 

ppt or less during the period of annual low freshwater flow. 

CHARACTERISTIC VEGETATION: Four variants of brackish marsh with reasonably distinct plant 

associations distributed along a hydrology and salinity gradient are described below. Eleocharis 

parvula (small spike-rush)* and Eleocharis halophila (salt-loving spike-rush)*, state-threatened 

species, can be found in brackish pannes on the Agrostis stolonifera var. palustris-Spartina 

patens-Juncus gerardii brackish marsh, throughout the Scirpus tabernaemontanii-Juncus 

arcticus var. littoralis and Typha angustifolia brackish marsh, or in wetter portions of the Carex 

paleacea brackish marsh. 

1. Low graminoid brackish marsh variant (Agrostis stolonifera var. palustris-Spartina 

patens-Juncus gerardii brackish marsh variant): This variant supports a greater diversity 

of plants and is generally flooded less frequently than other brackish marsh variants. It is 

vertically higher, receives more freshwater input, and experiences less frequent tidal 

flooding than the high salt marsh. It is characterized by a mix of graminoids including 

Agrostis stolonifera var. palustris (marsh creeping bent-grass), Spartina patens (saltmeadow 

cord-grass), and Juncus gerardii (salt marsh rush). One or more of these species 

may be locally dominant. 

Other common graminoids and forbs include Aster novi-belgii (New York aster), 

Solidago sempervirens (seaside goldenrod), Festuca rubra (red fescue), Spartina pectinata 


(fresh-water cord-grass), and Scirpus robustus (stout bulrush). Less constant and frequent 

plants include Juncus arcticus var. littoralis (shore rush), Polygonum ramosissimum (bushy 

knotweed), Elytrigia repens (quack-grass), Scirpus pungens (three-square rush), Distichlis 

spicata (spike-grass), Triglochin maritimum (arrow grass), Potentilla anserina 

(silverweed), Carex hormathodes (necklace sedge), Carex paleacea (chaffy salt sedge), 

Ranunculus sceleratus (cursed crowfoot), Panicum virgatum (switch-grass), Amaranthus 

cannabinus (water hemp), Hierochloe odorata (sweet grass), Elymus virginicus (Virginia 

wild rye), Teucrium canadensis (germander), Iris versicolor (northern blue flag), Cuscuta 

gronovii (Gronovius’ dodder), Impatiens capensis (spotted touch-me-not), Acorus calamus 

(sweetflag), Calystegia sepium (hedge bindweed), Poa pratensis (Kentucky bluegrass), 

Ligusticum scothicum (Scotch lovage), Typha angustifolia (narrow-leaved cat-tail), and 

Sanguisorba canadensis (Canadian burnet). The state-threatened Iris prismatica (slender 

blue flag)* occurs in this brackish marsh variant. 

Three types of pannes (small, temporary depressions isolated from tidal creeks) may 

occur within the relatively larger-sized Agrostis stolonifera var. palustris-Spartina 

patens-Juncus gerardii brackish marsh. 

a. Mixed forb panne: These shallow depressions are ponded only for short periods. 

Mixed forb pannes are characterized by a variable mix of graminoids and forbs 

including Scirpus pungens (three square rush), Triglochin maritimum (arrowgrass), 

Scirpus robustus (stout bulrush), Agrostis stolonifera var. palustris (marsh 

creeping bent-grass), Eleocharis halophila (salt-loving spike-rush)*, and 

Eleocharis parvula (small spike-rush)*. Less frequent are Festuca rubra (red 

fescue), Aster novi-belgii (New York aster), Potentilla anserina (silver-weed), 

Spartina patens (salt-meadow cord-grass), and Juncus gerardii (salt marsh rush). 

b. Typha angustifolia panne: This association includes small to moderate sized, 

ponded or saturated depressions dominated by Typha angustifolia (narrow-leaved 

cat-tail) within the low graminoid brackish marsh. Large areas of narrow-leaved 

cat-tail in a brackish marsh are best considered a Typha angustifolia brackish 

marsh and not a panne. See the description for the floristically similar Typha 

angustifolia brackish marsh for characteristic panne vegetation. 

c. Sparsely vegetated panne: These saturated to occasionally ponded, mud 

dominated pannes can occur adjacent to the forested upland where they are 

shaded by overhanging canopy branches. This is the usual habitat for the 

uncommon Ranunculus cymbalaria (seaside crowfoot), where prostrate colonies 

may form small patches over the soil surface. Other graminoids and forbs 

scattered across the mud, or more often around the panne edge, include Agrostis 

stolonifera var. palustris (marsh creeping bent-grass), Elymus virginicus (Virginia 

wild rye), Aster novi-belgii (New York aster), Solidago sempervirens (seaside 

goldenrod), Spartina alterniflora (smooth cord-grass), Carex paleacea (chaffy 

salt sedge), and Plantago major var. scopulorum (rock plantain). 


2. Medium graminoid brackish marsh variant (Carex paleacea brackish marsh variant): 

The Carex paleacea brackish marsh is floristically transitional and most similar to the 

Agrostis stolonifera var. palustris-Spartina patens-Juncus gerardii brackish marsh, but is 

dominated by Carex paleacea (chaffy salt sedge). Common associates include Scirpus 

robustus (stout bulrush), Agrostis stolonifera var. palustris (marsh creeping bent-grass), 

Spartina patens (salt-meadow cord-grass), Juncus gerardii (salt marsh rush), Festuca 

rubra (red fescue), Solidago sempervirens (seaside goldenrod), and Spartina pectinata 

(fresh-water cord-grass). The hydroperiod appears to be slightly wetter compared to that 

found in the Agrostis stolonifera var. palustris-Spartina patens-Juncus gerardii brackish 

marsh. 

3. Tall graminoid brackish marsh variant (Scirpus tabernaemontanii-Juncus arcticus 

var. littoralis brackish marsh variant): Scirpus tabernaemontanii-Juncus arcticus var. 

littoralis brackish marsh may occur along the upland edge of estuarine marshes in 

shallow, less frequently flooded depressions compared to other brackish marsh variants. 

Scirpus pungens (three-square rush), Typha angustifolia (narrow-leaved cat-tail), Carex 

paleacea (chaffy salt sedge), Phragmites australis (common reed; a native “weedy” grass 

in brackish marshes), Spartina pectinata (fresh-water cord-grass), and other species may 

be present. 

4. Robust forb brackish marsh variant (Typha angustifolia brackish marsh variant): The 

Typha angustifolia brackish marsh may occur along the upper edge of the high salt 

marsh, often in coves or other protected areas with restricted spring-tide “sheet flow” (bimonthly 

or less frequent tidal flooding event) and with significant freshwater input. Soils 

are ponded for longer periods compared to other variants of brackish marsh. Dead stems 

from the previous year are often thick above the hydrated soil surface. The Typha 

angustifolia brackish marsh may grade into a Typha angustifolia (narrow-leaved cat-tail) 

dominated high brackish tidal river-bank marsh on tidal streams and rivers where salinity 

levels are lower upstream and tidal flooding occurs several times a week (see description 

for high brackish tidal river-bank marsh). 

Narrow-leaved cat-tail dominates this variant of brackish marsh and may form a near 

monoculture in some examples. Associated plants may include Scirpus robustus (stout 

bulrush), Spartina patens (salt-meadow cord-grass), Lythrum salicaria (purple 

loosestrife), Phragmites australis (common reed), and less frequently Solidago 

sempervirens (seaside goldenrod), Aster novi-belgii (New York aster), Festuca rubra (red 

fescue), Scirpus pungens (three-square rush), Scirpus tabernaemontanii (soft-stemmed 

bulrush), Thelypteris palustris (marsh fern), Eleocharis flavescens var. olivacea (olivebrown 

spike-rush), Amaranthus cannabinus (water hemp), and several other brackish 

marsh species. In one example, Typha x glauca (hybrid cat-tail; Typha angustifolia x 

Typha latifolia) was the dominant cat-tail species in the brackish marsh. 



COMMENTS: This is a small patch community, variable in composition and usually found in 

association with basins characterized by restricted tidal influence or landward edges of high salt 

marsh where sufficient fresh water runoff or groundwater discharge flows onto the marsh surface. 

GOOD EXAMPLES: Squamscott River (Stratham, Exeter, Newfields); Blackwater and Hampton 

River Salt Marsh (Seabrook, Hampton Falls, Hampton). 

SOURCES: NH Heritage field surveys; Breeding, Richardson, and Pilgrim (1974). Prepared by 

Bill Nichols. 

• Coastal salt pond marsh (G4 S1) 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This community includes emergent marshes 

that are seasonally flooded with freshwater and periodically infused with salt water during storm 

events. It is presently known from a single site in New Hampshire. Water chemistry is 

characterized by a brackish to slightly brackish salinity and an average pH of 8.2. The marsh is 

separated from the coastal shoreline by a cobble ridge rising up to 12 ft. above mean sea level. 

The northern end of this ridge drops to approximately 7.5 ft. above mean sea level and shows 

recent evidence of wave action overtopping the barrier and depositing salt water and small 

amounts of sand into the marsh. The southern end of the cobble ridge is slightly higher (9-10 ft. 

above mean sea level) and has several furrows on its back side formed from breaching storm 

waves. 

SOILS/GEOLOGY/HYDROLOGY: The seasonally flooded soils consist of a 25 cm thick O horizon 

overlying a gravelly silt loam containing scattered coarse sand. Depth to bedrock (Rye 

Formation) in one soil pit was 35 cm. Scattered outcrops lie exposed in the marsh. 




ppt or less during the period of annual low freshwater flow. Salinity levels may fluctuate 

seasonally and over several years in response to freshwater input, evaporation, and periodic 

infusion with salt water during storm events. 

CHARACTERISTIC VEGETATION: Vegetation appears to be zonally distributed along water-related 

gradients (flooding/saturation duration and salinity). The marsh is dominated by clonal stands of 

Typha angustifolia (narrow-leaved cat-tail) and Scirpus tabernaemontanii (soft-stemmed 

bulrush). Lower areas exposed later in the growing season after draw-down are dominated by 

Eleocharis parvula (small spike-rush)*, in association with Eleocharis halophila (salt-loving 

spike-rush)*, Eleocharis flavescens var. olivacea (olive-brown spike-rush), Scirpus maritimus 

(alkali-bulrush), and Scirpus pungens (three-square rush). Spartina pectinata (fresh-water cordgrass) 

is abundant on higher ground along the basin edge. Other rare plants occurring in this 

marsh include Chenopodium rubrum (coast-blite)* and Zannichellia palustris (horned 

pondweed)*. Straus (1992) found horned pondweed was found here in 1992, but it was not seen 

in 1997. 


Other characteristic brackish marsh species include Plantago maritima (salt marsh plantain), 

Solidago sempervirens (seaside goldenrod), Phragmites australis (common reed), Agrostis 

stolonifera var. palustris (marsh creeping bent-grass), and Aster novi-belgii (New York aster). 

Many of these species occur in both fresh and brackish water habitats, but when found together, 

they denote brackish conditions. Several other species found only in freshwater habitats are 

restricted to higher ground along the basin edge where plant diversity is highest. The uncommon 

Lythrum hyssopifolia (hyssop-leaved loosestrife) and Spartina caespitosa (marsh cord-grass) 

also occur here. 

DISTRIBUTION: Odiorne Point State Park, Rye (Gulf of Maine Coastal Lowland subsection). 

COMMENTS: Composition and distribution of many of the plants are likely changing in response 

to variable precipitation and salt water intrusion during storm events. Other coastal salt pond 

marshes are likely to have occurred along the coast prior to development. 

GOOD EXAMPLES: Odiorne Point State Park (Rye), has the only known occurrence. 

SOURCES: NH Heritage field surveys; Straus (1992). Prepared by Bill Nichols. 

• Low brackish tidal river-bank marsh (S1S2) 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: Spartina alterniflora (smooth cord-grass) 

dominates the low brackish tidal river-bank marsh, a zone occurring between mean sea level and 

mean high tide typically along moderate to steep brackish tidal river- and stream-banks. The 

hydroperiod (duration and frequency of tidal flooding) roughly corresponds to that found in the 

low salt marsh. This community may grade into intertidal flats and subtidal communities toward 

the channel and high brackish tidal river-bank marsh landward. Where slopes are more gentle, 

the marsh may cover broader areas. As the sea level continues to rise (1–2 mm/year), brackish 

marsh may be submerged and replaced by salt marsh, while new areas suitable for brackish 

marsh may form landward. 

Marsh plant zonation results from several factors including ice-scouring, land use history, 

storms, hydroperiod, elevation of substrate, nutrient availability, salinity, soil oxygen, and 

biological interactions. Although many of these factors and processes, typically present as 

gradients, are often interrelated, they can vary at different rates or quantities (Zoltai and Vitt 

1995). Several rare plants restricted to brackish tidal rivers in New Hampshire occur here and in 

the adjacent high brackish tidal river-bank marsh. 




(Breeding et al. 1974). Substrate of smaller brooks near the upper reaches of the tidal influence 

are often gravelly or cobbly. 





ppt or less during the period of annual low freshwater flow. Salinity fluctuates widely in 

response to seasonal variation in freshwater discharge. 

CHARACTERISTIC VEGETATION: Spartina alterniflora (smooth cord-grass) typically dominates 

the physically stressful low marsh largely due to limited Compton from other plants, its tolerance 

of oligo- to euhaline soil water salinity, and an ability to oxygenate its roots and rhizosphere. As 

salinity decreases, Scirpus robustus (stout bulrush) and Typha angustifolia (narrow-leaved cattail) 

become more prominent and may dominate the low marsh in some examples. Associated 

vascular plants in low abundance may include Amaranthus cannabinus (water hemp), Atriplex 

hastata (halberd-leaved orach), Eleocharis parvula (small spike-rush)*, Eleocharis halophila 

(salt-loving spike-rush)*, Scirpus pungens (three-square rush), Scirpus maritimus (saltmarsh 

bulrush), Salicornia europaea (common glasswort), and Limonium carolinianum (sea lavendar). 

Rare plants that occur here and distinguish this community from low salt marshes include 

Limosella australis (mudwort)*, Lilaeopsis chinensis (Eastern lilaeopsis)*, Tillaea aquatica 

(pygmy weed)*, and Samolus parviflorus (water pimpernel)*. These rare species can also occur 

in the high brackish tidal river-bank marsh. Limosella australis (Atlantic mudwort)* may also 

be found on brackish intertidal flats. 

DISTRIBUTION: Restricted to brackish tidal stream and river margins in the Coastal Lowland 

subsection. 

COMMENTS: A narrowly defined community nearly always found in association with high 

brackish tidal river-bank marsh, often as a fairly narrow zone. 

GOOD EXAMPLES: Lamprey River Narrows (Newmarket); Salmon Falls River (Rollingsford); 

Bellamy River (Dover); Squamscott River (Exeter). 

SOURCES: NH Heritage field surveys. Prepared by Bill Nichols. 

• High brackish tidal river-bank marsh (S1S2) 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: High brackish tidal river-bank marshes 

typically occur as a narrow zone along moderate to steep brackish tidal river- and stream-banks 

flooded less than daily between the mean high water mark and the upper reaches of spring tides. 

The hydroperiod (duration and frequency of tidal flooding) roughly corresponds to that found in 

the high salt marsh. Where slopes are more gentle, the marsh may cover broader areas. This 

community may grade into low brackish tidal river-bank marsh, intertidal flats, and subtidal 

communities toward the channel. Fresh water wetlands or upland communities are found 

landward. As the sea level continues to rise (1–2 mm/year), brackish marsh may be submerged 

and replaced by salt marsh, while new areas suitable for brackish marsh may form landward. 

Although the water table is always at or relatively near the surface, tidal flooding decreases 

landward with increased elevation and microtopography, creating areas with higher soil oxygen 

that support a variety of species. This community supports brackish marsh species and other 


species most often found in fresh or salt marshes but tolerant of brackish conditions and able to 

successfully compete in this environment. Marsh plant zonation results from several factors 

including ice-scouring, land use history, storms, hydroperiod, elevation of substrate, nutrient 

availability, salinity, soil oxygen, and biological interactions. Although many of these factors 

and processes, typically present as gradients, are often interrelated, they can vary at different 

rates or quantities (Zoltai and Vitt 1995). Several rare plants restricted to brackish tidal rivers in 

New Hampshire occur here and in the adjacent low brackish tidal river-bank marsh. 




(Breeding et al. 1974). Substrate of smaller brooks near the upper reaches of the tidal influence 

are often gravelly or cobbly material. 

Soil water salinity generally ranged from greater than 0.5 parts per thousand (ppt) to less than 



ppt or less during the period of annual low freshwater flow. Salinity fluctuates widely in 

response to seasonal variation in freshwater discharge. 

CHARACTERISTIC VEGETATION: A variable mix of graminoids and forbs characterize this 

community including Scirpus robustus (stout bulrush), Aster novi-belgii (New York aster), 

Spartina patens (salt-meadow cord-grass), Juncus gerardii (salt marsh rush), Typha angustifolia 

(narrow-leaved cat-tail), Spartina pectinata (fresh-water cord-grass), Agrostis stolonifera var. 

palustris (marsh creeping bent-grass), Carex paleacea (chaffy salt sedge), Solidago sempervirens 

(seaside goldenrod), and Scirpus pungens (three-square rush). One or more of these species may 

be locally dominant. Less frequent species include Atriplex hastata (halberd-leaved orach), 

Cyperus filicinus (beach umbrella-sedge), Potentilla anserina (silver-weed), Sium suave (water 

parsnip), Calystegia sepium (hedge bindweed), Juncus arcticus var. littoralis (shore rush), 

Rumex crispus (curly dock), Plantago major var. scopulorum (rock plantain), Elytrigia repens 

(quack-grass), Distichlis spicata (spike-grass), Amaranthus cannabinus (water hemp), Festuca 

rubra (red fescue), Spartina alterniflora (smooth cord-grass), Elymus virginicus (Virginia wild 

rye), Poa pratensis (Kentucky bluegrass), Poa compressa (Canada bluegrass), Toxicodendron 

radicans (climbing poison ivy), Panicum virgatum (switch-grass), Carex hormathodes (necklace 

sedge), Hierochloe odorata (sweet grass), Lythrum salicaria (purple loosestrife), and 

Spergularia marina (seabeach sand-spurrey). Rare plants that occur here and distinguish this 

community from high salt marshes that have equivalent flood regime include Limosella australis 

(mudwort)*, Lilaeopsis chinensis (Eastern lilaeopsis)*, Tillaea aquatica (pygmy weed)*, and 

Samolus parviflorus (water pimpernel)*. These rare species can also occur in the low brackish 

tidal river-bank marsh. Limosella australis (Atlantic mudwort)* may also be found on brackish 

intertidal flats. 

DISTRIBUTION: Restricted to brackish tidal stream and river margins in the Coastal Lowland 

subsection. 


COMMENTS: A narrowly defined community nearly always found in association with low 

brackish tidal river-bank marsh, often as a fairly narrow zone. 

GOOD EXAMPLES: Lamprey River Narrows (Newmarket); Salmon Falls River (Rollingsford); 

Bellamy River (Dover); Squamscott River (Exeter). 

SOURCES: NH Heritage field surveys. Prepared by Bill Nichols. 

INTERTIDAL FLATS AND SHORES 

• Coastal shoreline strand/swale (S2) 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This is a sparsely vegetated upper intertidal 

community found on fine to coarse soils of protected estuarine shorelines or back dune sandy 

depressions and channels bordering salt marshes. The community is flooded less than daily and 

is often characterized by plant culms and other detritus washed in on the higher tides and 

covering much of the substrate surface. These upper intertidal areas form large patches or 

narrow strands along protected low-energy shorelines and are important habitat for various 

arthropods, shore birds, and other animals. 

SOILS/GEOLOGY/HYDROLOGY: The less than daily, tidally flooded substrate consists of fine to 

coarse soils or various types of bedrock including Rye Formation. 

CHARACTERISTIC VEGETATION: A sparse cover (typically

• Intertidal rocky shore (S3) 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: This is a sparsely vegetated intertidal 

community found on open stretches of estuarine rivers and streams or quiet, partially enclosed 

shores. Macroalgae is characteristic on rubble or bedrock substrates. This community may form 

large patches or narrow strands below the upper intertidal shoreline and is important habitat for 

various arthropods, predatory fish, wading birds, mud snails, and other animals. 

SOILS/GEOLOGY/HYDROLOGY: The daily tidally flooded substrate, exposed completely at extra 

low spring tide, primarily consists of coarse soils and/or various types of bedrock including Rye 

Formation. 




waters to waters occurring in Great Bay and its tributaries. Salinity levels in the Great Bay 

complex are generally greater than 20 parts per thousand (ppt) other than during major spring 

runoff events, whereas coastal areas remain closer to 30 ppt year-round (Short 1992). The 

upstream limit of this community occurs where salinity levels are 0.5 ppt or less during the 

period of annual low freshwater flow. 

CHARACTERISTIC VEGETATION: Macroalgae are often common on bedrock and rubble including 

Ascophyllum nodosum on larger outcrops and Fucus vesiculosus on less stable strata. 

DISTRIBUTION: Restricted to immediate shoreline areas of the Coastal Lowland subsection. 

COMMENTS: This community is distinguished from intertidal flat communities by a coarser soil 

particle size and firmer substrate and from high-energy marine intertidal rocky shores by reduced 

exposure to strong currents and wave-action. 

GOOD EXAMPLES: Odiorne Point State Park (Rye). 

SOURCES: NH Heritage field surveys; Short (1992). Prepared by Bill Nichols. 

• Saline/brackish intertidal flat (S3) 

GENERAL DESCRIPTION/ECOLOGICAL PROCESSES: Intertidal sand and mud flats are gently sloping, 

sparsely vegetated, habitats occurring between estuarine marshes (low salt marsh or low brackish 

tidal river-bank marsh) or other coastal communities landward and subtidal communities 

seaward. Tidal creek channels exposed at low tide are also included in this community. 

Intertidal flats form in depositional environments protected from high-energy wave action along 

the coast behind rocky spits, barrier beaches, and sand bars or along bays and rivers. These 

coastal landforms contribute sediments for intertidal flat formation. The substrate, exposed 

completely at extra low spring tide, ranges in composition from sand to mud and silt. 

Benthic diatoms and other microalgae occurring in this environment are important 

contributors to the primary productivity of the total estuarine system (Sickley 1989). Macroalgae 


is typically uncommon across the exposed substrate. Characteristic invertebrates found in New 

Hampshire's intertidal mud flats include polychaete worms (including Nereis virens, Nephtys 

caeca, Clymenella tortquata, and Scoloplos spp.) and mollusks (including soft-shelled clam 

(Mya arenaria), Baltic Macoma (Macoma balthica), gem shell (Gemma gemma), and swamp 

Hydrobia (Hydrobia minuta)) (Normandeau Associates 1973). Arthropods are also well 

represented and include green crabs (Carcinus maenus), rock crabs (Cancer irroratus), flatclawed 

hermit crabs (Pagurus pollicaris), and horseshoe crabs (Limulus polyphemis). During the 

diurnal (twice daily) tidal flooding several species of fish and other aquatic species feed on the 

benthos and epibenthic algae. This community also provides important foraging habitat for 

shorebirds and other animals when the intertidal flat is exposed. The diverse variety of primary 

foods (microalgae, phytoplankton, and detritus) available to consumers supports the high 

productivity found on intertidal flats. 

SOILS/GEOLOGY/HYDROLOGY: The daily tidally flooded substrate is composed of sand or silt and clay 

rich in organic matter. Muds contain a greater percentage of organic matter than sands. Coarser 

sediments are deposited in areas exposed to greater wave action and higher currents (channels, 

beaches, and inlet mouths) while finer particles are deposited in lower energy environments (higher 

intertidal elevations and areas at increasing distances from inlet mouths) (Redfield 1972). Ice action 

during winter months can also influence sediment accretion, erosion, and transport. 




waters to waters occurring in Great Bay and its tributaries. Salinity levels in the Great Bay 

complex are generally greater than 20 parts per thousand (ppt) other than during major spring 

runoff events, whereas coastal areas remain closer to 30 ppt year-round (Short 1992). The 

upstream limit of this community occurs where salinity levels are 0.5 ppt or less during the 

period of annual low freshwater flow. 

CHARACTERISTIC VEGETATION: Vascular plants are sparse to more typically absent. Brackish 

flats may support populations of Eleocharis parvula (small spike-rush)* and Limosella australis 

(Atlantic mudwort)*. A total of 169 seaweed species have been documented in the Great Bay 

Estuary including the Piscataqua River (144 spp.), Little Bay (132 spp.), Great Bay proper (90 

spp.), and ranging from four to 49 species in the seven tidal rivers entering Great Bay (Mathieson 

and Penniman 1991). 


COMMENTS: This community is distinguished from coastal shoreline strand/swales by the 

absence or very sparse cover of vascular plants and more frequent tidal flooding. Intertidal flats 

differ from intertidal rocky shores by a finer soil texture and less firm substrate. 

GOOD EXAMPLES: Seaward of the Blackwater and Hampton River Salt Marsh (Seabrook, 

Hampton Falls, Hampton); Great Bay and vicinity. 

SOURCES: Short (1992); Whitlatch (1982); NH Heritage field surveys. Prepared by Bill Nichols. 


SUBTIDAL COMMUNITIES 

(SALINE/BRACKISH SUBTIDAL CHANNEL/BAY BOTTOM COMMUNITIES) 

This group of communities occurs in permanently flooded, saline or brackish, tidal channels 

and bays. Intertidal flats or rocky shores exposed at low tide along the drainage margin are 

described under saline/brackish intertidal flat or intertidal rocky shore. Vascular plants are 

typically absent or sparse. A lens of freshwater may flow over heavier brackish water. Salinity 

can fluctuate widely as the boundary between the two water layers rises and falls as it moves 

upstream or downstream with the tides. 

These communities perform important ecological functions including supporting oyster, 

eelgrass, and flounder populations, providing refuge for fish and invertebrates that retreat from 

eelgrass beds, intertidal flats, and estuarine marshes at low tide, and serving as a spawning and 

nursery area for numerous species of aquatic animals (Short 1992). 

• Undifferentiated saline/brackish subtidal channel/bay bottom (S3) 

CHARACTERISTIC VEGETATION: Vascular plants are typically absent or sparse. Seaweeds are an 

important component of this habitat and the surrounding environment. A total of 169 seaweed 

species have been documented as occurring in the Great Bay Estuary including the Piscataqua 

River (144 species), Little Bay (132 species), Great Bay proper (90 species), and a range of four 

to 49 species in the seven tidal rivers entering Great Bay (Mathieson and Penniman 1991). 

Common species include Gracilaria tikvahiae (the most abundant algae), Fucus vesiculosus 

(rockweed), Laminaria spp. (kelp), Ascophyllum nodosum (rockweed), and Chondrus crispus 

(Irish moss). Enteromorpha spp. and Ulva lactuca (sea lettuce) are also present and considered 

to be indicators of eutrophication. Several species of seaweed within Great Bay are disjunct 

from populations south of Cape Cod (Short 1992). These include Gracilaria tikvahiae, Bryopsis 

plumosa, Dasya baillouviana, Chondria tenuissima, Lomentaria clavellosa, Lomentaria 

orcadensis, and Polysiphonia subtilissima. Several marine and estuarine invertebrates also have 

a similar disjunct distributional pattern (Bousfield and Thomas 1975; Turgeon 1976). These 

disjunct plants and animals are either relics of a time when coastal waters were warmer 

(Bousfield and Thomas 1975) or are introduced from the south. 

SOILS/GEOLOGY/HYDROLOGY: Water salinity generally ranges from greater than 0.5 parts per 

thousand (ppt) to less than 30 ppt (mixohaline). Salinity fluctuates widely according to seasonal 

variation in freshwater discharge with greater variation occurring within the Great Bay complex 

than in estuaries closer to the coast (Short 1992). There is also a pattern of decreased surface 

water salinity from coastal areas to those occurring in Great Bay and its tributaries. Salinity 

levels in the Great Bay complex are generally greater than 20 parts per thousand (ppt) other than 

during major spring runoff events, whereas coastal areas remain closer to 30 ppt year-round 

(Short 1992). Substrates vary at different locations and include mud, sand, gravel, cobble, or 

rock. 

DISTRIBUTION: Restricted to subtidal channels and bays of the Coastal Lowland subsection. 


COMMENTS: Where salinity levels are 0.5 ppt or less during the period of annual low freshwater 

flow, freshwater tidal rivers and streams may occur. The construction of dams across brackish 

sections of the state’s major tidal rivers probably eliminated examples of this community type 

that may once have occurred in New Hampshire. 

GOOD EXAMPLES: Lamprey River Narrows (Newmarket), Salmon Falls River (Rollingsford), 

Bellamy River (Dover), Squamscott River (Exeter), Berry’s Brook (Rye), and Great Bay. 

SOURCES: NH Heritage field surveys; Short (1992). Prepared by Bill Nichols. 

• Tidal creek bottom (S3) 

This community occurs in permanently flooded creek-bottoms draining water from the high 

and low salt marsh into a main channel or bay. The substrate is composed of mud rich in organic 

matter. Portions of tidal creeks exposed at low tide are described under saline/brackish intertidal 

flat. Vascular plants are sparse but may include Ruppia maritima (widgeon-grass). Tidal creeks 

provide habitat for stickleback (Pungitius pungitius, Gasterosteus aculeatus, and Apeltes 

quadracus), mummichog (Fundulus heteroclitus), and several other species of fish (Short 1992) 

and foraging ground for migratory and year round bird species and other animals. As salt 

marshes replace accreting intertidal flats seaward, tidal creeks develop along former intertidal 

flat drainage channels. Landward, as the high salt marsh develops above mean high water, tidal 

flooding frequency decreases, reducing drainage flow in the creeks. This tends to cause the 

upstream end of the tidal creek to fill in as sediment deposition occurs at a greater rate than 

erosion (Redfield 1972). The banks of tidal creeks are nearly vertical and often slump, 

supporting a narrow band of Spartina alterniflora (smooth cord-grass) (see low salt marsh 

description). Good examples of this community occur in the Blackwater and Hampton River 

Salt Marsh (Seabrook, Hampton Falls, Hampton). 

• Eelgrass bed (S1) 

Shallow subtidal populations of Zostera marina (eelgrass) characterize this community. 

Eelgrass beds occur in estuarine waters on mud rich in organic matter or sand bottoms. This 

rooted aquatic vascular plant covers nearly half of the bottom of Great Bay (2585 acres) (Short 

1992). Eelgrass beds trap sediments, dissolved nutrients, and larval organisms flowing through 

the community (Thayer et al. 1975; Short and Short 1984) and are an important contributor to 

ecosystem health and productivity. They serve as breeding, nursery, and feeding areas for many 

species of fish and invertebrates. This community also provides foraging grounds for waterfowl 

and wading birds that feed on the eelgrass or the fish and invertebrates the beds harbor. Eelgrass 

is both a contributor to and indicator of the general health of an estuary. Excessive nutrient 

levels entering an estuary from fertilizers, waste-water effluent, and other sources are 

incorporated into the leaf tissue of eelgrass. When nutrient levels become too high however, 

phytoplankton and epiphytes can shade out and eliminate eelgrass beds (Short 1992). The upper 

limits of eelgrass populations are determined in large part by ice scour in winter and desiccation 


in summer (Costa 1988). Daily period of light penetration above a physiological minimum 

threshold regulates the maximum depth (Dennison and Albert 1986). Light penetration is a 

function of depth and concentration of suspended particles. In the northeast, eelgrass can grow 

to a depth of 6 m (20 ft.) where water transparency is high. Good examples of eelgrass beds 

occur in shallow subtidal areas of Great Bay. 

• Oyster bed 

Crassostrea virginica (oyster) beds occur in shallow mixohaline estuarine waters of the Great 

Bay complex. The largest beds are found within the upper Piscataqua River and near Nannie 

Island while the southwest portion of Great Bay supports the highest oyster densities (Short 

1992). Oysters are an important food source for many other animals including starfish, crabs, 

fishes, and waterfowl. 

Unlike other natural communities described in this document, oyster beds do not contain 

rooted vegetation, so they should be treated in a classification of unvegetated estuarine subtidal 

systems. We include it here because oyster beds are an integral part of broader estuarine 

systems, including the natural communities described above. 


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table of contents - New Hampshire Division of Forests and Lands

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