The Natural Communities of Virginia
Classification of Ecological Community Groups
SECOND APPROXIMATION (Version 2.4)
Information current as of June, 2011
Interdune Ponds
Interdune Ponds are seasonally to semipermanently flooded, maritime herbaceous wetlands occupying deep interdune basins and swales. Examples are known from New Jersey south to North Carolina, but the complete range is uncertain. In Virginia these wetlands are distributed very locally in zones behind barrier beaches from the Eastern Shore (Accomack and Northampton Counties) to Cape Henry and False Cape (City of Virginia Beach). This ecological group includes both freshwater ponds, in which rainwater and groundwater quickly dilutes infrequent salt-water inputs, and slightly brackish ponds subject to more frequent salt water inputs. The latter, which appear to have salinity regimes that vary over time from entirely fresh to slightly mesohaline, are probably best characterized as oligohaline ponds. Community composition varies with geography, topographic position, exposure to storm surges and salt spray, hydroperiod, and soil properties. In general, types occurring in Virginia can be considered very locally distributed, small-patch wetlands that are state-rare. Seasonally flooded, freshwater ponds usually contain large cover of bulrushes (e.g ., Scirpus cyperinus, Schoenoplectus pungens var. pungens, Schoenoplectus tabernaemontani), grasses (e.g., Panicum virgatum var. virgatum, Panicum rigidulum var. condensum, Spartina patens), or squarestem spikerush (Eleocharis quadrangulata). Rare freshwater ponds, or their marginal zones, are dominated by nearly pure stands of twig rush (Cladium mariscoides). Seasonally flooded oligohaline ponds may be dominated by narrow-leaved cattail (Typha angustifolia), eastern rose-mallow (Hibiscus moscheutos ssp. moscheutos), or saltmarsh bulrush (Schoenoplectus robustus, = Scirpus robustus), compositionally resembling Tidal Oligohaline Marshes. Semipermanently flooded oligohaline ponds are dominated by coastal water-hyssop (Bacopa monnieri), white spikerush (Eleocharis albidum), and sago pondweed (Stuckenia pectinata , = Potamogeton pectinatus). Reference: The Nature Conservancy (1997).
Click on the images below to open a larger image in a separate window.
|
Switchgrass (Panicum virgatum var. virgatum) and giant plumegrass (Saccharum giganteum) in a freshwater pond among eroded back dunes near Ragged Point on Assateague Island, Accomack County (Chincoteague National Wildlife Refuge). Photo: Gary P. Fleming / © DCR Natural Heritage. |
 |
Spatterdock (Nuphar advena) and swamp loosestrife (Decodon verticillatus) in an interdune pond First Landing / Seashore State Park, City of Virginia Beach. In some years, the exposed, peaty shores of this pond are carpeted with bog-loving species such as spoon-leaved sundews (Drosera intermedia). Photo: Gary P. Fleming / © DCR Natural Heritage. |
 |
A large, oligohaline dune pond behind the frontal dunes near Swan Cove on Assateague Island, Accomack County (Chincoteague National Wildlife Refuge). The vegetation here is depauperate, with huge mats of coastal water-hyssop (Bacopa monnieri) dominating and only three additional species occurring in small numbers. Photo: Gary P. Fleming / © DCR Natural Heritage. |
REPRESENTATIVE COMMUNITY TYPES:
Communities in this group need more intensive study and classification is incomplete. Plot data have been collected from False Cape State Park in southeastern Virginia, Chincoteague National Wildlife Refuge on the Eastern Shore, and a few other sites (map), but have not yet been systematically analyzed by DCR-DNH ecologists. Field notes from several additional occurrences describe vegetation of a different composition that needs to be targeted for future plot-sampling. Chincoteague plots were used by NatureServe ecologists to produce the first two USNVC associations listed below. Click on any highlighted CEGL code below to view the global USNVC description provided by NatureServe Explorer.
- (Myrica cerifera) - Panicum virgatum - Spartina patens Herbaceous Vegetation
Interdune Pond (Switchgrass Freshwater Type)
USNVC:CEGL004129
Global/State Ranks: G2G4/S2?
- Bacopa monnieri - Eleocharis albida Herbaceous Vegetation
Interdune Pond (Coastal Water-Hyssop - White Spikerush Oligohaline Type)
USNVC:CEGL006350
Global/State Ranks: G1Q/S1
- Typha angustifolia - Hibiscus moscheutos Herbaceous Vegetation
Interdune Pond (Narrow-Leaved Cattail - Eastern Rose-Mallow Type)
USNVC: no equivalent
Global/State Ranks: -/SU
| back to top of page | next Ecological Group | previous Ecological Group |