Mountain / Piedmont Basic Seepage Swamps
Gently sloping stream headwaters, large spring seeps, and lateral areas in ravines and stream bottoms where groundwater emerges at the base of slopes are the characteristic habitats for the saturated deciduous forests of this group. These communities are locally scattered throughout western Virginia at elevations up to 975 m (3,200 ft) in areas underlain by metabasalt (greenstone) and other mafic rocks, base-rich granitic rocks, calcareous shale, and limestone. They are most common on the northern Blue Ridge but are found occasionally in the Ridge and Valley province, and rarely in the western Piedmont. Habitats usually have considerable cover of bouldery, cobbly, and gravelly alluvium; braided seeps and stream channels; moss (except Sphagnum)-covered hummocks; and muck-filled depressions. Soils range from strongly acidic to circumneutral, with moderately high calcium and magnesium levels.
Overstory composition is mixed, with variable combinations of red maple (Acer rubrum), white ash (Fraxinus americana), black ash (Fraxinus nigra), tulip-tree (Liriodendron tulipifera), and sweet birch (Betula lenta var. lenta). Yellow birch (Betula alleghaniensis) is an important tree at some sites. Spicebush (Lindera benzoin var. benzoin) is usually the most abundant shrub. Herbaceous cover is typically lush, and often features patch-dominance of skunk cabbage (Symplocarpus foetidus), American false-hellebore (Veratrum viride), and/or sedges (especially Carex bromoides ssp. bromoides and Carex prasina). Additional characteristic herbs include marsh marigold (Caltha palustris), golden saxifrage (Chrysosplenium americanum), swamp saxifrage (Micranthes pensylvanica), lettuce saxifrage (Micranthes micranthidifolia), marsh blue violet (Viola cucullata), golden ragwort (Packera aurea = Senecio aureus), orange jewelweed (Impatiens capensis), water-hemlock (Cicuta maculata var. maculata), large purple fringed orchid (Platanthera grandiflora), and various ferns. Most Virginia populations of the globally rare plants bog bluegrass (Poa paludigena) and glade spurge (Euphorbia purpurea), as well as of the globally rare Blue Ridge Mountain amphipod (Stygobromus spinosus), are associated with these swamps.References: Fleming (1999), Fleming and Coulling (2001).
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Mountain / Piedmont Basic Seepage Swamp along a spring-fed tributary of Goose Creek at Banshee Reeks Nature Preserve in Loudoun County. This is one of a few examples of the community type found in the western Piedmont region. Photo: Gary P. Fleming / © DCR Natural Heritage.
Marsh marigold (Caltha palustris) and skunk cabbage (Symplocarpus foetidus) dominate the early spring herbaceous flora of a basic seepage swamp on the northern Blue Ridge. Headwaters of Wildcat Hollow, Fauquier County (G. Richard Thompson Wildlife Management Area). Photo © Gary P. Fleming.