Ohio subset of Plant Communities of the Midwest ... - NatureServe

* Nonstandard type (needs review)
Great Lakes Coastal Wetlands Complex*
Great Lakes Coastal Wetlands Complex
Open and Emergent Marshes: Great Lakes Coastal Marshes and Complex
Great Lakes Coastal Wetlands Complex
CECX002002
DESCRIPTION: This Great Lakes Coastal Wetlands Complex is found throughout the Great Lakes Basin and upper
St. Lawrence Valley in the United States and Canada. These coastal wetlands have recently been characterized in
detail by a series of studies summarized by Minc and Albert (1998). The following summary has largely been
abstracted from their work.
The Great Lakes coastal wetlands occur along the Great Lakes shoreline proper and in portions of tributary rivers and
streams that are directly affected by Great Lakes water regimes. Species distributions and community patterns are
determined by multiple abiotic factors, including the type of aquatic system (whether lacustrine, connecting major
river channels, smaller tributary rivers, or estuarine), Great Lakes water-level fluctuations, surficial bedrock, glacial
landform, climate, and land use. Great Lakes water level fluctuate over at least three temporal time scales: first,
short-term fluctuations caused by winds or barometric pressures; second, seasonal fluctuations reflecting the annual
hydrologic cycle in the basin; and third, interannual fluctuations in lake level as a result of variable precipitation and
evaporation within the drainage basin. Interannual fluctuations can be as much as 1.3-2.5 m, with apparently little or
no periodicity. These fluctuations, which also alter turbidity, nutrient availability, ice scour zones, etc., cause locational
shifts in vegetation zones, but also in the composition of these zones, as species have individual tolerance limits.
The major bedrock distinction in the Great Lakes Basin is between igneous and metamorphic bedrock of the
Precambrian period and younger (Paleozoic) sedimentary bedrock. The igneous and metamorphic bedrock form the
rugged north shore of Lake Superior and Georgian Bay, and line much of the St. Lawrence River; they are locally
present on the south shore of western Lake Superior. They lack the shallow protected waters and fine-textured
substrates that support broad coastal wetlands. Where such bedrock is at or near the surface, it forms soils that are
nutrient-poor and acidic. The rest of the basin is dominated by softer, sedimentary bedrock, which, with its broad,
horizontal depositions, favors broad zones of shallow waters. The sedimentary rocks are typically more alkaline
(calcareous), forming soils that are nutrient- and moisture-rich loams and clays.
Bedrock patterns are overlaid by glacial landforms that, in combination with recent long-shore transport processes,
create the prevalent physiographic features of the shorelines. In the lakes themselves, sand lakeplains, clay
lakeplains, and moraines are shaped by currents, and the long-shore transportation of sediments has created sandspit
embayments and swales, dune-swale complexes, and tombolos. Channels and rivers contain channel-side
wetlands, embayments, and deltas, and estuaries form as either open or barred river mouths. It is this diversity of
landforms that has given rise to a diverse set of vegetation types.
Finally, regional patterns of climate affect the basin. The strong latitudinal gradient from southern Lake Erie to
northern Lake Superior creates marked differences in length of growing season and solar radiation. Although wetland
species are generally widely distributed, those of more boreal and subarctic regions are found in the northern parts of
the basin, whereas those of more temperate and prairie regions are found in the southern parts.
Vegetation types found across this diverse set of abiotic factors vary in any number of ways, but they can be placed
into a number of zones, though not all are present at a given site. The first four zones are typically inundated directly
by lake waters: (a) submergent marsh - containing submergent and/or floating vegetation; (b) emergent marsh -
characterized by shallow water or semipermanently flooded soils, and typically dominated by bulrushes, cattails, and
other emergent species, but also containing submergent and/or floating vegetation; (c) shore fen - saturated
vegetation mats characterized by groundwater influence from shoreline habitats but affected by lake level
fluctuations, and dominated by herbaceous or shrubby species; (d) shoreline or strand - a narrow zone at or just
above the water level where seasonal water-level fluctuations and waves cause erosion, and which is dominated by
annual or pioneer herbaceous species. The next set of zones are inland from the water's edge and include: (e)
herbaceous and shrubby wet meadows - characterized by saturated or seasonally flooded soils, and typically
dominated by sedges, grasses, and other herbs, but occasionally dominated by shrubs; and (f) shrub or wooded
swamps - characterized by seasonal flooding and dominated by woody species. Species assemblages in these
zones change depending on the interaction of factors across the Great Lakes Basin. The data gathered by Minc and
Albert (1998) indicate that it is possible to divide the zones into a number of different vegetation types, or
associations. The submergent and emergent marsh zones can each be divided into two types: Northern Great Lakes
Submergent Marsh, Potamogeton gramineus - Potamogeton natans Northern Great Lakes Shore Herbaceous
Vegetation (CEGL005273); Southern Great Lakes Submergent Marsh, Potamogeton zosteriformis - Ceratophyllum
demersum - Elodea canadensis Southern Great Lakes Shore Herbaceous Vegetation (CEGL005152); Northern
Great Lakes Emergent Marsh, Schoenoplectus acutus - Schoenoplectus subterminalis - Eleocharis palustris -
PLANT COMMUNITIES OF THE MIDWEST – 2001. APPENDIX: ASSOCIATION DESCRIPTIONS
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