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Wetland Plants and Plant Communities of Minnesota and Wisconsin

VI.A. HARDWOOD SWAMPS


Hardwood swamps are dominated by deciduous hardwood trees and have soils that are saturated during much of the growing season, and may be inundated by as much as a foot of standing water (Shaw and Fredine 1971). Dominant trees include black ash, red maple, yellow birch and, south of the vegetation tension zone, silver maple. Northern white cedar can be a subdominant species in stands within and north of the vegetation tension zone. American elm is still an important component of this community, although its numbers have been greatly reduced by Dutch elm disease. These communities are commonly found on ancient lake basins. Vernal pools often occur in wooded swamps.

The shrub layer of hardwood swamps is often composed of shrub-size individuals of the dominant tree species, as well as the dogwoods and alder species of shrub swamps. Groundlayer species include some of the ferns, sedges, grasses and forbs of sedge meadows and fresh (wet) meadows. Refer to the species listed under those communities.

A hardwood swamp

VEGETATION: This hardwood swamp is dominated by black ash (Fraxinus nigra) with a groundlayer dominated by lake sedge (Carex lacustris), ostrich fern (Matteuccia struthiopteris) and marsh marigold (Caltha palustris). Other species present: red maple (Acer rubrum), yellow birch (Betula alleghaniensis), speckled alder (Alnus incana ssp. rugosa), American black currant (Ribes americanum), cinnamon fern (Osmunda cinnamomea), sensitive fern (Onoclea sensibilis), fowl manna grass (Glyceria striata), fowl bluegrass (Poa palustris), wood reedgrass (Cinna latifolia), jewelweed (Impatiens capensis), jack-in-the-pulpit (Arisaema triphyllum), giant goldenrod (Solidago gigantea), redstem aster (Aster puniceus), water parsnip (Sium suave) and purple-fringed orchis (Platanthera psycodes). Bog bluegrass (Poa paludigena), a species listed as threatened by the State of Minnesota, occurs in this habitat. The above photograph was taken in May when marsh marigolds were in full bloom.

SOILS: Rondeau muck (Limnic Borosaprists), a very poorly-drained calcareous muck with an organic layer 16 to 51 inches in depth overlaying marl. Landscape position of the example shown above is a broad terrace of the St. Croix River valley.

HYDROLOGY: Groundwater discharge (seepages). Rondeau muck is typically saturated to the surface and may have up to 12 inches of standing water. The example shown is not subject to inundation by flood events as it is located at an elevation well above the St. Croix River floodplain.

LOCATION: Pine County, Minnesota.

SPECIES ACCOUNTS:

Black Ash (Fraxinus nigra Marsh.)
Red Maple (Acer rubrum L.)
Yellow Birch (Betula alleghaniensis Britton)
Quaking Aspen (Populus tremuloides Michx.)
Ostrich Fern (Matteucia struthiopteris L.)
Skunk Cabbage (Symplocarpus foetidus (L.) Nutt.)
Marsh Marigold (Caltha palustris L.)
Purple-fringed Orchis (Platanthera psycodes (L.) Lindl.)
Jewelweed (Impatiens capensis Meerb.)


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