Plant Communities of the Midwest - NatureServe

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groupings, such as “forested peatlands,” “fen,” “shrub swamp,” “coniferous woodland,” or “cliff” (e.g., White and Madany 1978, Nelson 1985, Reschke 1990, Minnesota Natural Heritage Program 1993). In Ontario, Lee et al. (1998) also used ecological categories at higher levels (“community class” and “community series”) above their vegetation types. In Canada, something similar to an ecological groups approach was used to define wetland types (National Wetlands Working Group 1988). The Working Group used five broad wetland classes to organize wetland types: bog, fen, swamp, marsh, and shallow open water. Their reason for retaining familiar terms for broad ecological groups is worth highlighting: “It is not surprising that a close examination shows that there are many subtly or substantially different definitions of these terms. One solution is to abandon them completely......the other solution is to define them, keeping in mind the possibility of other usage…” Cowardin et al. (1979) chose the former approach; the Wetlands Working Group chose the latter, as did we. Thus, even though users will be familiar with many of the terms used for ecological groups, we recommend that all users read the definitions (see Table 5) to ensure that they understand the usage intended here. Midwestern ecological groups were developed using the above-mentioned sources. A first draft was outlined in 1999 in consultation with the southeastern regional ecology teams of both ABI and the Conservancy, who had also begun to experiment with an ecological groups approach. In August of 2000, both teams began to work closely together to resolve differences, at least at the finest level. That work was completed late in 2000. As a result, the ecological groups approach presented below has been integrated across both regions. The groups are experimental and still need more review, both at state/provincial levels and globally. Currently, each association is reported in only one ecological group; that is, the groups are mutually exclusive. In this way the groups facilitate the listing of associations in this report. 2 However, individual alliances are often divided among ecological groups. This is not surprising, given that alliances are typically defined by patterns of dominant canopy species, which often range quite widely across environmental conditions. STRUCTURE Overview Ecological groups are defined based on habitat, ecological processes, vegetation and biogeography. Criteria vary somewhat among groups, but generally groups share similar macro- to mesoclimate, geology/parent material, substrate, and physiognomy. The ecological groups are organized hierarchically into four levels above the association. Given the preliminary nature of this hierarchy, the levels have not been formally named; instead, they are numbered from 1 (broadest) to 4 (finest) (Table 4). Level 2 groups form the backbone of the system and each is defined in Table 5. 2 However, associations could be listed under multiple ecological groups, depending on how those groups are defined. In what could be termed a more “systems-based” approach, ecological groups would be defined based more on their spatial relationships and shared processes than on similar vegetation. For example, currently the “Midwestern Riverfront Floodplain Forests” group contains associations that are all found in floodplains (Table 6). There are also several more generic wetland ecological groups, such as “Midwestern Rich Shrub Swamps” and “Midwestern Wet Prairies and Meadows,” whose associations are found in both floodplains and in upland depression wetlands (the same association may be found in both settings). Using the “systems-based” approach, the “Midwestern Riverfront Floodplain Forests” group could be generalized to be a “Midwestern Riverfront Floodplains” system that includes forest, shrubland, and marsh associations that are often spatially contiguous and that share similar floodplain processes. Since the same shrubland and marsh associations that occur in floodplains also occur in upland depressional wetlands, they would be listed under other system types encompassing those wetlands. Such an approach, which may be termed an “ecological systems” approach, is currently being considered by the Conservancy and ABI. PLANT COMMUNITIES OF THE MIDWEST – 2001 20
Table 4. Definitions and criteria used to define the various levels of ecological groups. Level 1. This level is more or less the “System Level” of Cowardin et al. (1979). This level differentiates the uplands from all types of wetlands, and differentiates among the wetland types in terms of their major hydrologic, geomorphic, chemical and biological factors, separating freshwater palustrine wetlands from tidal marine and estuarine wetlands (see Cowardin et al. 1979). Ecological groups only cover the vegetated or sparsely vegetated parts of these systems. Lakes and rivers are not included. Note that some wetland associations are placed within upland groups, in cases where they occur together spatially with upland assocations (e.g., 2.1. Shoreline Sand/Mud Strands, Beaches and Dunes). Level 2. Among the wetland types, the primary distinctions are based on hydrology, water quality and vegetation physiognomy. Peatlands (defined as wetlands with a peat depth of at least 30 cm) are divided at this level into acid peatlands and rich fens. Other types include seeps, marshes, wet prairies and meadows, and wooded swamps and floodplains (swamps may contain both minerotrophic peatlands and mineral soils). Among the upland types, the primary distinctions are based on parent material and substrate type and their interaction with physiognomy. Groups with parent material or parent mineral material (sand, clays) extensively exposed at the surface, and with up to 60% herbaceous, shrub, or tree cover (e.g., cliffs, talus slopes), are separated from types where sufficient mineral soil exists to permit a more or less complete cover (> 60% cover of the dominant strata of vegetation), whether herbaceous, shrub, or tree-dominated. Level 3. Both upland and wetland types are grouped by floristic and ecoregionally-based categories. The categories used are based on the division and province level ecoregions of the U.S. Forest Service ECOMAP (Bailey et al. 1994, Keys et al. 1995), as interpreted from a midwestern perspective, within the larger framework of Takhtajan’s floristic province level (Figure 4). • The “Northern (Laurentian)” group more or less equates to Province 212 (Bailey 1994). “Laurentian,” a term used by Bailey, is used to qualify “Northern” from a North American perspective. • “Great Lakes” refers to shoreline or near-shoreline communities around the Great Lakes. • “Midwestern” includes the central and northern (primarily glaciated) portion of Province 222 and much of Province 251, the Tallgrass Prairie Region. • “Interior Highlands” includes the Ozarks and Interior Low Plateau, both unglaciated. • The Appalachian Highlands include the areas of Provinces 221 (Allegheny and Cumberland Regions) M221 (the Appalachian Mountains), and Section 231A (the Piedmont). • “Southeastern” equates more or less with Province 232. • “Great Plains” equates to Division 330. • “Rocky Mountains” includes the Black Hills. Level 4. A variety of factors are used to distinguish groups at this level. In many cases physiognomy is important, e.g., Northern (Laurentian) Acid Peatlands are separated into Conifer versus Shrub/Graminoid groups. Other factors include dominant species, substrate, or water salinity. Level 5. The association. This is the lowest level of the classification and is taken from the USNVC hierarchy (Grossman et al. 1998). PLANT COMMUNITIES OF THE MIDWEST – 2001 21
Page 1: PLANT COMMUNITIES OF THE MIDWEST CL
Page 4 and 5: ISBN 0-9711053-0-8 © 2001 Associat
Page 6 and 7: This work has also benefited from i
Page 8 and 9: LISTS OF TABLES AND FIGURES List of
Page 10 and 11: Figure 1a. Distribution of alvar si
Page 12 and 13: (most associations were defined and
Page 14 and 15: particularly in Indiana and western
Page 16 and 17: y ABI and the Natural Heritage Netw
Page 18 and 19: Table 2. Illustration of the USNVC
Page 20 and 21: to year. In addition, the same asso
Page 22 and 23: journal articles, books, agency rep
Page 24 and 25: Once the cross-walk and review of t
Page 26 and 27: peatland, Great Lakes dune-swale co
Page 30 and 31: Table 5. Definitions of ecological
Page 32 and 33: Level 1 distinguishes wetland ecolo
Page 34 and 35: PLATE 2 1. 1.4. Open and Emergent M
Page 36 and 37: PLATE 4 1. 2. 2.1. Shoreline Sand/M
Page 38 and 39: PLATE 6 2. 3. 1. 2.3. Rocky Uplands
Page 40 and 41: PLATE 8 1. 2. 2.5. Forests and Wood
Page 42 and 43: PLATE 10 1. 2. 2.9. Prairies/Grassl
Page 44 and 45: PLATE 12 Map of The Nature Conserva
Page 46 and 47: Great Plains Northern (Laurentian)
Page 48 and 49: Table 6. Ecological groups for the
Page 50 and 51: Grassland Forest and Woodland Prair
Page 52 and 53: High Tp w Woodland Only Mean Annual
Page 54 and 55: Box 1. Summary of information used
Page 56 and 57: Table 9. A list of plant communitie
Page 58 and 59: 1.4. OPEN AND EMERGENT MARSHES 1.4.
Page 60 and 61: 1.5.5.3. Great Plains Prairie Potho
Page 62 and 63: 1.6.4.5. Southeastern Coastal Plain
Page 64 and 65: 2.3.1.2. Northern Acid Rock Outcrop
Page 66 and 67: 2.4.3.5. Eastern Alkaline Talus Lim
Page 68 and 69: 2.5.2.3. Midwestern Mesic Hardwood
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Page 72 and 73: 2.8.3. Interior Highlands Oak Savan
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Jenkins, R. 1996. Natural Heritage
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Sneddon, L., M. Anderson, and K. Me
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