Coastal Plain / Piedmont Acidic Seepage Swamps
The habitats occupied by these saturated, deciduous or mixed forests include small headwaters stream bottoms and seeping toe-slopes with acidic, nutrient-poor soils. Similar seepage wetlands are known from most coastal states of the mid-Atlantic region from New York south. In Virginia, communities of this group are scattered throughout the more dissected, inner Coastal Plain and outer Piedmont in habitats where seepage discharged at ground surface is drained away as stream flow. Characterized by diffuse drainage with braided channels and Sphagnum-covered hummocks in a sandy or peaty substrate, these habitats are generally wet and somewhat protected from fire. Dominant overstory species are red maple (Acer rubrum) and blackgum (Nyssa sylvatica), with tulip-tree (Liriodendron tulipifera) and loblolly pine (Pinus taeda) also locally important. Common small trees and shrubs are sweetbay magnolia (Magnolia virginiana), sweet pepperbush (Clethra alnifolia), highbush blueberries (Vaccinium spp.), swamp azalea (Rhododendron viscosum), smooth winterberry (Ilex laevigata), and southern wild raisin (Viburnum nudum). Compact dodder (Cuscuta compacta) is often abundantly attached to the stems of shrubs in these swamps. Common herbaceous species include cinnamon fern (Osmundastrum cinnamomeum var. cinnamomeum), netted chain fern (Woodwardia areolata), and the sedges Carex lonchocarpa and Carex seorsa. Less widespread herbaceous species that could be considered more or less diagnostic (within the Coastal Plain context) include skunk cabbage (Symplocarpus foetidus), kidney-leaved grass-of-parnassus (Parnassia asarifolia), Collins's sedge (Carex collinsii), twining bartonia (Bartonia paniculata ssp. paniculata), and the federally listed swamp-pink (Helonias bullata). Several uncommon odonates (dragonflies and damselflies) depend on forested seeps for breeding habitat. Coastal Plain / Piedmont seepage swamps are relatively small in size and threatened by beaver activities, agricultural pollutants, hydrologic disturbances, and logging. The treatment of these communities and the very similar Mountain / Piedmont Acidic Seepage Swamps as separate ecological groups may be revised in the future.References: McCoy and Fleming (2000), Rawinski (1995).
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Sweetbay magnolia (Magnolia virginiana) and cinnamon fern (Osmundastrum cinnamomeum var. cinnamomeum) in a dense acidic seepage swamp near Fredericksburg, Spotsylvania County (Fredericksburg-Spotsylvania National Military Park). Photo: Gary P. Fleming.
Coastal Plain / Piedmont Acidic Seepage Swamp southeast of Varina Grove near Malvern Hill, Henrico County (Richmond National Battlefield). Photo: Gary P. Fleming.