Piedmont / Mountain Floodplain Forests
These temporarily and intermittently flooded forests encompass most river floodplain habitats of the Piedmont and major mountain valleys, except those that are cleared or occupied by swamp forests. From the James River north, sandy river banks and first-bottom terraces that are frequently (but shortly) flooded support forests dominated by silver maple (Acer saccharinum) and boxelder (Acer negundo var. negundo), with herb layers containing many broad-leaved forbs such as wood-nettle (Laportea canadensis), clear-weed (Pilea pumila), and white snakeroot (Ageratina altissima var. altissima). Higher, better drained, sandy or silty river floodplains support mixed forests of sycamore (Platanus occidentalis), black walnut (Juglans nigra), hackberry (Celtis occidentalis), American elm (Ulmus americana), and boxelder, with understories of paw-paw (Asimina triloba) and spicebush (Lindera benzoin var. benzoin). Herb layers in the mixed floodplains are usually very lush with nutrient-demanding, early-season species such as Virginia bluebells (Mertensia virginica), Canada waterleaf (Hydrophyllum canadense), wild ginger (Asarum canadense var. canadense), yellow trout-lily (Erythronium americanum ssp. americanum), white trout-lily (Erythronium albidum), Potomac River only), wild blue phlox (Phlox divaricata ssp. divaricata), miami-mist (Phacelia purshii), large solomon's-seal (Polygonatum biflorum var. commutatum), striped violet (Viola striata), and many others. Eastern cottonwood (Populus deltoides ssp. deltoides) is a frequent, early-successional pioneer of these habitats, while sycamore and river birch (Betula nigra) are pioneering invaders of stabilized depositional river bars.
In the Piedmont south of the James River, silver maple is infrequent and river bottoms usually support mixed stands of green ash (Fraxinus pennsylvanica), American elm, hackberries (Celtis occidentalis and Celtis laevigata), sycamore, sweetgum (Liquidambar styraciflua), red maple (Acer rubrum), bitternut hickory (Carya cordiformis), and hydrophytic oaks (e.g ., willow oak [Quercus phellos], Shumard oak [Quercus shumardii)]). Small tree, shrub, and herbaceous composition is highly variable with geography and site conditions.
Most Piedmont/Mountain Floodplain Forests have been severely impacted by clearing, grazing, agricultural run-off, and invasive introduced weeds. Many of these forests have been destroyed and few, if any, of the remaining stands are in excellent or pristine condition.References: Fleming (2002a), Fleming (2007), Fleming and Coulling (2001), Fleming and Patterson (2004), Lea (2000), Rawinski et al . (1996), Vanderhorst (2000).
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Virginia bluebells (Mertensia virginica) dominate the vernal herb layer of a rich floodplain forest along the Shenandoah River in Clarke County. Photo: © Gary P. Fleming.
Silver maples (Acer saccharinum) line the banks of the James River, while sycamore (Platanus occidentalis) and river birch (Betula nigra) dominate the lower-lying island beyond. Hardware River Wildlife Management Area, Fluvanna County. Photo © Gary P. Fleming.
Canada waterleaf (Hydrophyllum canadense) is a patch-dominant herb in rich, well-drained floodplain forests of the Potomac Gorge west of Washington, D.C. Turkey Run Park, Fairfax County. Photo: Gary P. Fleming / © DCR Natural Heritage.
Flooded silver maple (Acer saccharinum) stand on the Potomac River. Wood nettle (Laportea canadensis) is the prominent herb in the foreground. Scotts Run Nature Preserve, Fairfax County. Photo: Karen D. Patterson / © DCR Natural Heritage.