Department of Conservation and Recreation

THE NATURAL COMMUNITIES OF VIRGINIA
CLASSIFICATION OF ECOLOGICAL COMMUNITY GROUPS

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Second Approximation (Version 2.5)
Information current as of February, 2012

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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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Click on the images below to open a larger image in a separate window.

	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.

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REPRESENTATIVE COMMUNITY TYPES:
This group is currently represented by 65 Virginia plot samples, many of them from floodplains of the Potomac, Shenandoah, and James Rivers (map). Classification of two community types (the Central Appalachian Silver Maple Forest and Central Appalachian Rich Floodplain Forest) is relatively robust and supported by a Virginia-Maryland-D.C. dataset of 90 plots. Floodplain forests of the Rappahannock, Appomattox, Roanoke, New, and Clinch Rivers and their major tributaries are either unsampled or grossly under-represented by plot data. Click on any highlighted CEGL code below to view the global USNVC description provided by NatureServe Explorer.

• Acer saccharinum - Acer negundo / Ageratina altissima - Laportea canadensis - (Elymus virginicus, Elymus macgregoryi) Forest
  Piedmont / Central Appalachian Silver Maple Forest
  USNVC: = CEGL006217
  Global/State Ranks: G4/S4
  
  
• Platanus occidentalis - Acer negundo - Juglans nigra / Asimina triloba / Mertensia virginica Forest
  Piedmont / entral Appalachian Rich Floodplain Forest
  USNVC: = CEGL004073
  Global/State Ranks: G4/S3S4
  
  
• Acer saccharum - Fraxinus americana - Carya cordiformis / Erythronium americanum Forest
  Piedmont / Central Appalachian High Terrace Floodplain Forest
  USNVC: = CEGL006459
  Global/State Ranks: G3?/S1
  
  
• Betula nigra - Platanus occidentalis Forest
  Piedmont / Central Appalachian River Birch - Sycamore Forest
  USNVC: = CEGL002086
  Global/State Ranks: G5/SU
  
  
• Quercus rubra - Quercus shumardii - Fraxinus americana / Cercis canadensis Forest [Provisional]
  Potomac Gorge Bedrock Floodplain Oak Forest
  USNVC: = CEGL006495
  Global/State Ranks: GNR/SU
  

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