Department of Conservation and Recreation
Conserve. Protect. Enjoy.
Department of Conservation and Recreation
Table of ContentsMountain / Piedmont Seepage Swamps
This group of saturated, forested wetlands occupies gently sloping stream headwaters, large spring seeps, and lateral areas in ravines and stream bottoms where groundwater emerges at the base of slopes. These communities are locally scattered throughout western Virginia, from the lowest elevations to well over 1200 m (4,000 ft). Habitats typically have hummock-and-hollow microtopography, with considerable cover of bouldery, cobbly, and gravelly alluvium; braided seeps and stream channels; moss-covered hummocks; and muck-filled depressions. Hydrologically, these habitats are classified as "groundwater slope wetlands," where seepage discharged at the ground surface is drained away as stream flow. They differ from certain basin wetlands that are saturated strictly by perched groundwater and support somewhat similar vegetation (see the Montane Depression Swamps and Ponds ecological group description for more information). The six community types separate along gradients of soil and groundwater chemistry, elevation, and geography.
The Central Appalachian Basic Seepage Swamp occurs 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. The type is most common on the northern Blue Ridge but is found occasionally in the Ridge and Valley province, and rarely in the western Piedmont. 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 var. palustris), golden saxifrage (Chrysosplenium americanum), swamp saxifrage (Micranthes pensylvanica), lettuce saxifrage (Micranthes micranthidifolia), marsh blue violet (Viola cucullata), golden ragwort (Packera aurea), 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 basic-soil swamps.
Acidic analogues of the preceding type occur in the same region on soils weathered from sandstone, quartzite, or base-poor granitic rocks. Abundant Sphagnum mats and groundwater with low pH are typical habitat features. Soils are very strongly to extremely acidic, with low base status. Composition is variable over the range of this group. Red maple (Acer rubrum), blackgum (Nyssa sylvatica), and tulip-poplar (Liriodendron tulipifera), are the most typical trees, while winterberry (Ilex verticillata), swamp azalea (Rhododendron viscosum var. viscosum), highbush blueberries (Vaccinium corymbosum and Vaccinium fuscatum) are abundant shrubs. Pitch pine (Pinus rigida) is a characteristic tree of some Ridge and Valley stands. Skunk-cabbage (Symplocarpus foetidus) and American false-hellebore (Veratrum viride) may be as dominant in these communities as in Mountain / Piedmont Basic Seepage Swamps; herbs and low shrubs more abundant in or characteristic of acidic swamps include cinnamon fern (Osmundastrum cinnamomeum), bristly dewberry (Rubus hispidus), kidneyleaf grass-of-parnassus (Parnassia asarifolia), yellow fringed orchid (Platanthera ciliaris) small green wood orchid (Platanthera clavellata), common tree clubmoss (Lycopodium obscurum), white-edged sedge (Carex debilis), and long sedge (Carex folliculata). Like the very similar Coastal Plain / Piedmont Acidic Seepage Swamps, these communities support populations of the federally listed swamp-pink (Helonias bullata).
Seepage swamps above 975 m (3,200 ft) elevation are compositionally allied with more northern vegetation types. Eastern hemlock (Tsuga canadensis), yellow birch (Betula alleghaniensis), and red maple (Acer rubrum) are the most common trees. Locally, red spruce (Picea rubens) or eastern white pine (Pinus strobus) may be co-dominants. Shrub layer composition and density is variable; deciduous hollies (Ilex verticillata and Ilex montana), several blueberries (particularly Vaccinium corymbosum, Vaccinium simulatum, and Vaccinium angustifolium), great rhododendron (Rhododendron maximum), mountain laurel (Kalmia latifolia), speckled alder (Alnus rugosa), and witch hazel (Hamamelis virginiana var. virginiana) may be abundant. Characteristic herbs of these swamps include marsh marigold (Caltha palustris var. palustris), star sedge (Carex echinata ssp. echinata), finely-nerved sedge (Carex leptonervia), eastern rough sedge (Carex scabrata), three-seeded sedge (Carex trisperma), slender wood reedgrass (Cinna latifolia), tall flat-topped white aster (Doellingeria umbellata var. umbellata), spinulose wood fern (Dryopteris carthusiana), slender mannagrass (Glyceria melicaria), whorled wood aster (Oclemena acuminata), cinnamon fern (Osmundastrum cinnamomeum), American false-hellebore (Veratrum viride), and smooth white violet (Viola mackloskeyi var. pallens). Communities in this group are naturally rare due to the scarcity of flat or gentle, wet habitats in the higher Appalachians.
All seepage swamps are small-patch communities susceptible to hydrological disturbances. Beavers have partially destroyed fine examples of these swamps at several sites, and the integrity of many stands has been compromised by extensive hemlock mortality due to outbreaks of hemlock woolly adelgid (Adelges tsugae). Currently, the abundant ash component of the Central Appalachian Basic Seepage Swamp is suffering significant mortality from outbreaks of Emerald Ash Borer.
References: Allard and Leonard (1943), Carr (1939), Fleming (1999), Fleming (2002b), Fleming and Van Alstine (1990, Fleming and Coulling (2001), Rawinski et al. (1994), Rawinski et al. (1996).Click here for more photos of this ecological community group.
© DCR-DNH, Gary P. Fleming.
Download a spreadsheet of compositional summary statistics for each of the community types listed below.
