Piedmont Upland Depression Swamps
Communities in this group generally occur on nearly level Piedmont uplands with clay hardpan subsoils, from south-central Maryland south to South Carolina. In Virginia, these wetlands are scattered throughout the eastern and central Piedmont. They are most numerous in Mesozoic basins and areas underlain by mafic rocks or acidic slates. Habitats include shallow, seasonally flooded upland basins, as well as broad, wet bottoms along small streams. Because of low relief, headwater drainages in parts of the Piedmont are very diffuse, with sluggish, usually intermittent flows and no active alluvial deposition. Within this physiographic context, it can be difficult to distinguish true isolated wetland basins from "non-alluvial" stream bottoms. Hydrologically, these topographically divergent habitats are comparable, with shallow seasonal flooding induced by perched water tables during the winter and spring months. Hydroperiods, however, can apparently be irregular and unpredictable. Maximum flooding depth is usually < 25 cm (10 in). A-horizon soils are dark brown to blackish, loamy clays which typically exhibit pronounced orange and white mottling.
Canopy cover ranges from complete to very open. In northern Virginia, pin oak (Quercus palustris), swamp white oak (Quercus bicolor), red maple (Acer rubrum) and, to a lesser extent, willow oak (Quercus phellos) are characteristic. In the southern Piedmont, willow oak, sweetgum (Liquidambar styraciflua), and overcup oak (Quercus lyrata) are typical. Shrub composition is variable but usually includes an abundance of climbing common greenbrier (Smilax rotundifolia). The herb layer is often sparse; common species include sedges (especially Carex festucacea and Carex albolutescens in the southern Piedmont, and Carex pellita in the northern Piedmont), common wood reedgrass (Cinna arundinacea), Virginia cutgrass (Leersia virginica), manna-grasses (Glyceria spp.), and rushes (Juncus spp). American tree moss (Climaceum americanum) and, in more acidic habitats, Sphagnum mosses (Sphagnum spp.) frequently form large patches on slightly raised hummocks.
Upland depression swamps are isolated and semi-isolated wetlands subject to major disturbances and alterations from logging, draining, and development. All community types in the group are considered globally and/or state-rare.
Reference: Fleming (2002a), Fleming and Patterson (2004), Fleming and Weber (2003).Click here for more photos of this ecological community group.
© DCR-DNH, Gary P. Fleming.