Floodplain Ponds and Pools
Semipermanently to permanently flooded ponds or pools are uncommon natural features of major Coastal Plain and Piedmont floodplains. These wetlands are typically developed in abandoned oxbows and cut-off meanders, ranging in size from less than 0.01 ha to about four ha (0.2 to 10 ac). Community composition is probably influenced by a combination of environmental factors, including flooding regime, water depths, soil fertility, and degree of shading. Dominant vegetation varies from woodland and shrublands in shallower, semipermanently flooded ponds to submerged or floating aquatics in deeper ponds. Scattered bald cypress (Taxodium distichum), tupelos (Nyssa aquatica and Nyssa biflora), green ash (Fraxinus pennsylvanica), or red maple (Acer rubrum) are sometimes rooted in large Coastal Plain oxbow ponds. More often, shrublands dominated by buttonbush (Cephalanthus occidentalis) or swamp loosestrife (Decodon verticillatus) are established. In the more deeply flooded ponds, aquatic species prevail, with or without scattered shrubs and emergents such as Virginia chain fern (Woodwardia virginica), sedges (Carex spp.), and eastern mannagrass (Glyceria septentrionalis). Typical aquatics include common mermaid-weed (Proserpinaca palustris), bladderworts (Utricularia spp.), spatterdock (Nuphar advena), duckweeds (Lemna spp.), duckmeats (Spirodela spp.), northern water-starwort (Callitriche heterophylla), watershield (Brasenia schreberi), hornworts (Ceratophyllum spp.), waterweeds (Elodea spp.), American frog's-bit (Limnobium spongia), pondweeds (Potamogeton spp.), Carolina mosquito-fern (Azolla caroliniana), milfoils (Myriophyllum spp.), and shade mudflower (Micranthemum umbrosum).At least two aquatic plants found in these communities, yellow water crowfoot (Ranunculus flabellaris) and featherfoil (Hottonia inflata), are state-rare or uncommon. Although apparently more often associated with beaver ponds (see Semipermanent Impoundments), non-tidal emergent marshes are present in large oxbows of the Pamunkey River in eastern Virginia. Wetlands in this group are important breeding habitats for turtles and amphibians, including the state-rare mole salamander (Ambystoma talpoideum). Well-developed floodplain ponds and pools appear to be rather rare communities in need of much additional inventory and study.
Reference: Fleming (2007), Walton et al. (2001).
Click on the images below to open a larger image in a separate window.
|Non-tidal marsh vegetation and scattered clumps of buttonbush (Cephalanthus occidentalis) in an old oxbow pond along the Pamunkey River in Hanover County. Photo: Dean Walton / © DCR Natural Heritage|
|Spatterdock (Nuphar advena) in Black Pond on a bedrock terrace along the Potomac River in Fairfax County. This very rare landform and natural community developed in a Pleistocene oxbow well above the current channel shelf. Photo: Gary P. Fleming / © DCR Natural Heritage.|
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