The Natural Communities of Virginia
Classification of Ecological Community Groups
SECOND APPROXIMATION (Version 2.2)
Riverine Aquatic Beds
The floating and submergent herbaceous vegetation of this group inhabits flowing streams with water depths that exclude emergent species but
permit bottom rooting of aquatic species. These communities occur throughout the eastern United States. They are poorly inventoried in Virginia,
but are known to occur in rocky shallows along many of the major mountain and Piedmont rivers. They are particularly well developed in base-rich
waters of the Shenandoah River (including its two forks), the James River, and portions of the Roanoke River. Characteristic species include
grass-leaf mud-plantain (
Heteranthera dubia), American eel-grass (
Vallisneria americana), pondweeds (
Potamogeton
spp.), waterweeds (
Elodea canadensis and
Elodea nuttallii), and waternymphs (
Najas spp.). Horn-leaf riverweed
(
Podostemum ceratophyllum) is often abundantly rooted on shallowly submerged boulders and rock outcrops. Sluggish shoreline eddies
and pools often support mats of floating duckweeds (
Lemna spp.), duckmeats (
Spirodela spp.), and Carolina mosquito-fern
(
Azolla caroliniana). Water pollution is a serious threat that can cause major declines or die-offs of aquatic vegetation in this group.
Click on the images below to open a larger image in a separate window.
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An aquatic bed dominated by grass-leaved mud-plantain (Heteranthera dubia, with yellow flowers)
and Illinois pondweed (Potamogeton illinoensis, with wide leaves) covers the James River in Buckingham County.
Photo © Irvine Wilson.
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REPRESENTATIVE COMMUNITY TYPES:
The two community types nested under this group are based on existing associations in the USNVC and are broadly
consistent with stands observed by VANHP ecologists along inland rivers (
e.g., the Potomac, Shenandoah, and James) in the
northern half of Virginia. Inventory of this group is clearly needed, although it is limited by accessibility issues and difficulties in
quantitative sampling and will likely be considered a relatively low priority by VANHP in the near future.
Click on any highlighted CEGL code below to view the global USNVC description provided by
NatureServe Explorer.
- Podostemum ceratophyllum Herbaceous Vegetation
Riverine Aquatic Bed (Horn-Leaf Riverweed Type)
USNVC:
CEGL004331
Global/State Ranks:
G5/SNR
- Vallisneria americana Riverine Herbaceous Vegetation
Riverine Aquatic Bed (American Eel-Grass Type)
USNVC:
CEGL004333
Global/State Ranks:
G3G4/SNR
