This group encompasses aquatic and shoreline vegetation of both beaver ponds and persistent man-made impoundments (e.g., millponds) along streams in all regions of Virginia. Compared to communities in the Floodplain Ponds and Pools group, semipermanent impoundments are more subject to unpredictable disturbances from flooding, beaver activities, irregular water fluctuations, and breaching of dams. Over time, or more rapidly when drained, these wetlands tend to fill with sediment and undergo invasion by emergent and woody vegetation. Community composition varies greatly with geographic region, disturbance regimes, substrate and water depth. Emergent, non-tidal marshes are characteristic of abandoned but persistent beaver ponds. Dominant species of such marshes in the Coastal Plain include smartweeds (Persicaria spp.), pickerelweed (Pontederia cordata var. cordata), arrow-arum (Peltandra virginica), common rush (Juncus effusus), three-way sedge (Dulichium arundinaceum var. arundinaceum), tussock sedge (Carex stricta), spikerushes (Eleocharis spp.), coastal mannagrass (Glyceria obtusa), Virginia marsh St. John's-wort (Hypericum virginicum), and swamp rose-mallow (Hibiscus moscheutos). In the Piedmont and mountains, American bur-reed (Sparganium americanum), arrow-arum (Peltandra virginica), sedges (Carex spp.), lizard's-tail (Saururus cernuus), common water-purslane(Ludwigia palustris), alternate-leaved seedbox (Ludwigia alternifolia), common cattail (Typha latifolia), southern water-plantain (Alisma subcordatum), woolgrass (Scirpus cyperinus), woodland bulrush (Scirpus expansus), and rice cutgrass (Leersia oryzoides) are more characteristic.
In deepwater impoundments, floating and submerged aquatic plants are typical, including white water-lily (Nymphaea odorata ssp. odorata) and bladderworts (Utricularia spp.) in the Coastal Plain, and common spatterdock (Nuphar advena), water shield (Brasenia schreberi), pondweeds (Potamogeton spp.), large water-starwort (Callitriche heterophylla var. heterophylla), and duckweeds (Lemna spp.) state-wide. Rare peaty or sandy Coastal Plain ponds with abundant seepage inputs support state-rare species such as water bulrush (Schoenoplectus subterminalis), Robbins' spikerush (Eleocharis robbinsii), horsetail spikerush (Eleocharis equisetoides), purple bladderwort (Utricularia purpurea), and big floating heart (Nymphoides aquatica).Reference: Coulling (2002), McCoy and Fleming (2000), Walton et al . (2001).
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Floating aquatic vegetation, including eastern mosquito fern (Azolla caroliniana), swamp water-pennywort (Hydrocotyle ranunculoides), and smooth bur-marigold (Bidens laevis), in Sunken Meadow Pond, an old Coastal Plain millpond near Claremont, Surry County. Photo: Gary P. Fleming / © DCR Natural Heritage.