Plant Communities of the Midwest - NatureServe

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(most associations were defined and reviewed by the Natural Heritage Network prior to 1999); as such, the ecological groups are experimental and need more review. Our main objective is to provide a classification and description of natural plant communities found in the Midwest. The information is based on a combination of literature review, data analyses, existing classification documents, expert opinion, and peer review from colleagues throughout the Natural Heritage Network, many of whom have contributed their time and expertise in reviewing the material presented here. Each description provides a link to the state classifications used by Natural Heritage programs. The description also includes an assessment of the rarity and rangewide distribution of the type, which is consistent with the mission of ABI to apply this classification to conservation issues. II. A BRIEF INTRODUCTION TO THE ECOLOGICAL REGIONS OF THE MIDWEST The Midwestern Region covers a twelve state area in the northcentral United States, totaling some 752,000 square miles (1,946,000 square kilometers). Canada forms the border to the north. The Central Lowlands Province dominates the physiographic landscape of the Midwest. It extends westward to the Great Plains and eastward to the Allegheny Plateau (southeastern Ohio). Southward, it is bordered by the Interior Highlands (Interior Low Plateau and Ozark Plateau), which is divided by the northern extension of the Mississippi River Alluvial Plain into the bootheel of Missouri and adjacent Illinois. Northward, the Central Lowlands extend into the mixed conifer-hardwood region around the Great Lakes, except for a small part of northern Wisconsin and northeastern Minnesota that are on the Canadian Shield. An integrated perspective on the ecological diversity of the region is provided by ecological land classifications of the region. Among the best developed and most widely used is that of Robert Bailey (1995, 1998), who has produced a series of ecoregional maps (Bailey et al. 1994, 1998). To address issues of scale, Bailey’s system is hierarchical, distinguishing four ecological levels—domain, division, province, and section—at increasingly finer levels of scale. Finer scale units, such as the subsection level, have been developed by others (Keys et al. 1995). Units at each level are established based on interacting biotic and abiotic factors. Macroclimate is the principal factor used to identify continental-scale regions at the division and domain levels. Climatic subzones, assessed in part by broad-scale vegetation formations, form the basis for subdividing the divisions into provinces. Mountain provinces are those that exhibit altitudinal zonation within a shared climatic division of the adjacent lowland (in the Midwest these occur only in the Black Hills on the South Dakota - Wyoming border). Within provinces, landforms exert the major control over climate, and are used to subdivide the provinces into sections (Bailey 1995). The ecoregional map for the Midwest displays broad climatic and vegetation formation gradients across the regions, as well as some of the major landforms that shape regional vegetation patterns. The ecological features (including landforms, soils, climate, and vegetation) of these regions are described down to the province level by Bailey (1995) and at the section level by McNab and Evers (1994) (see also Plate 11). Great Plains Region The Great Plains (Temperate Steppe Division) contains two provinces (see Plate 11). This semiarid continental climate has cold and dry winters with warm to hot summers. Precipitation ranges from about 10 inches (26 cm) in the north and west (Province 331) to as much as 30 inches (77 cm) along the eastern portions of Nebraska and Oklahoma (Province 332). Evaporation typically exceeds precipitation. The Black Hills, geologically a part of the Rocky Mountains, are tall enough (7200 feet) to create a mountain climate. At higher elevations they contain montane grasslands, ponderosa pine (Pinus ponderosa) and white spruce (Picea glauca) forests. Mixedgrass prairie or steppe (0.5 to 1 m tall) dominates the northern parts of the Great Plains. Dominants include western wheatgrass (Pascopyrum smithii), green needle-and-thread (Hesperostipa comata), little bluestem (Schizachyrium scoparium) and side-oats grama (Bouteloua curtipendula). The central and southern parts of Province 331 transition to PLANT COMMUNITIES OF THE MIDWEST – 2001 4
shortgrass prairies, where the vegetation rarely exceeds 0.5 m. Dominants there include blue grama (Bouteloua gracilis) and buffalo grass (Buchloe dactyloides). Much of the landscape consists of rolling plains and tablelands, but some extensive badlands formations occur in the White River Badlands of South Dakota and the Little Missouri Badlands of western North Dakota (Section 331F). Soils are primarily Mollisols and can be quite saline (or haline). The northern part of Province 332 and adjacent parts of 331E were glaciated (more or less north of the Missouri River), creating geologically young, glacially-derived soils and dissected till plains. Water is much more extensive, and prairie potholes are numerous. South of the Missouri River, loess and sand deposits cover much of the area, including the large Sandhills region of western Nebraska (Section 332C). Eastern cottonwood (Populus deltoides) and green ash (Fraxinus pennsylvanica) are common floodplain trees. Drought, fires, and grazing herbivores (e.g., prairie dogs, bison) have historically influenced the vegetation. Prairie Parkland Region Within the Prairie Division, the Prairie Parkland Province extends southward from the Canadian border to Oklahoma and extends eastward in the “prairie peninsula” to northwest Indiana (see Plate 11). The subhumid climate varies in annual precipitation from 20 to 40 inches (51 to 100 cm), with precipitation and evaporation more or less equal. Soils are primarily Mollisols. In the northern regions glaciation has left extensive rolling glacial till uplands and prairie potholes. Southward, soils vary from loess (sometimes formed into Loess Hills east of the Missouri River in Iowa) to thin soils over bedrock, especially in the Flint Hills region of Kansas and Oklahoma (Section 251F). The vegetation in this climate is a mixture of deciduous (especially oak) forest, woodland, savanna, and grassland (or prairie). Prairies are dominated by tall grasses, often 1 to 2 m tall. Big bluestem (Andropogon gerardii), yellow Indian grass (Sorghastrum nutans), little bluestem (Schizachyrium scoparium), switchgrass (Panicum virgatum), prairie dropseed (Sporobolus heterolepis), and porcupine grass (Hesperostipa spartea) are common. The alternation of these types in the western part of the parkland is partly a function of the local soil conditions and slopes; forests and woodlands are restricted to more moist and well-protected areas. In the eastern part of the parkland, forests and woodlands are more widespread, but prairies and savannas predominate in the flattest and most exposed areas. Fire and grazing (and more recently, haying) play a critical role in the balance between prairie and woodland. Floodplains are dominated by eastern cottonwood (Populus deltoides) and green ash (Fraxinus pennsylvanica), along with willows and oaks. Eastern Dry Deciduous (Broadleaf) Forests Region This dry (or continental) eastern deciduous forest region is part of the Hot Continental Division, where hot summers and cool winters prevail (see Plate 11). In this province (222), precipitation varies from 20 inches (51 cm) on the western edge to over 40 inches (100 cm) in the east. Most of the central area has rolling topography that was mostly glaciated, but some parts are nearly flat. The soils show some degree of podzolization and are typically Alfisols. Further south in the Ozark Highlands region (Section 222A), the relief is moderate, up to 1,000 feet (300 m). Low rolling hills and dissection plateaus are found in the Interior Low Plateau region (Sections 222D, E, and F). Together, these two unglaciated regions are sometimes referred to as the Interior Highlands. Ultisols tend to predominate. The vegetation across this province is dominated by broadleaf, deciduous hardwoods, including sugar maple (Acer saccharum) and American basswood (Tilia americana), but the dry conditions towards the west tend to favor a diverse mix of oaks and hickories, which are often less than 60 feet (20 m) tall. Northward the oaks are typically white oak (Quercus alba), northern red oak (Quercus rubra), black oak (Quercus velutina) and bur oak (Quercus macrocarpa). Southward (especially in the unglaciated border regions), these mix with post oak (Quercus stellata) and blackjack oak (Quercus marilandica). Prairie and savannas predominate in the border regions with the Prairie Parkland (especially in Sections 222A, 222G, 222K, 222M, and 222N). The dissected regions of the Interior Highlands often have open cliffs and rocky ledges with grassy or scrubby glade communities. The Paleozoic Plateau (or Driftless Area) in Section 222L is more dissected and favorable to forested conditions. Further east in the province, PLANT COMMUNITIES OF THE MIDWEST – 2001 5
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 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 28 and 29: groupings, such as “forested peat
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
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1.6.4.5. Southeastern Coastal Plain
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2.3.1.2. Northern Acid Rock Outcrop
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2.4.3.5. Eastern Alkaline Talus Lim
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2.5.2.3. Midwestern Mesic Hardwood
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2.5.6. Rocky Mountains Forests and
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2.8.3. Interior Highlands Oak Savan
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PLANT COMMUNITIES OF THE MIDWEST -
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Bliss, L. C. and G. W. Cox. 1964. P
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Jenkins, R. 1996. Natural Heritage
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Sneddon, L., M. Anderson, and K. Me
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