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NATURAL HERITAGE

THE NATURAL COMMUNITIES OF VIRGINIA
CLASSIFICATION OF ECOLOGICAL COMMUNITY GROUPS


Second Approximation (Version 2.6)
Information current as of July, 2013



High-Energy Tidal River Shores

This ecological group encompasses small-patch herbaceous vegetation of narrow tidal flats, shores, bars, and channel edges in the low intertidal zone along major tidal rivers and their larger tributaries. Tidal fluctuations, as well as turbulence, flushing, and substrate scouring from waves, wind, and ice, are more pronounced in these habitats than in the adjacent marshes and appear to be stronger correlates of vegetation composition than does prevailing salinity regime. Substrates occupied by vegetation of this group are relatively coarse for the tidal class, ranging from mixtures of sand, silt, clay, and pebbles to coarse gravel and cobbles with low organic matter content. However, the soils of somewhat lower-energy channel edges may consist of mucky clay and very fine silt with higher organic matter. The habitats are generally exposed at low tide but remain inundated during spring tides.

Vegetation of high-energy tidal shores varies from sparse to dense, but tends to be low-statured (< 1 m tall, often much less). Unlike most marshes, these communities occur in linear patches, chiefly < 10 m wide, and most occur under both freshwater and oligohaline regimes. Composition appears to vary with substrate and other environmental dynamics. Species of bulrush, particularly common threesquare (Schoenoplectus pungens var. pungens) and soft-stem bulrush (Schoenoplectus tabernaemontani), are characteristic of most sites. Common threesquare dominates gravelly shores of the tidal Potomac River in northern Virginia, where ice scouring is most frequent. Vegetation of sandy habitats subject to greater periodic turbulence tends to be sparse and contain low annuals and perennials such as shore quillwort (Isoetes riparia), Parker's pipewort (Eriocaulon parkeri), dotted smartweed (Persicaria punctata), dwarf arrowhead (Sagittaria subulata), grass-leaved arrowhead (Sagittaria graminea), American waterwort (Elatine americana), flatsedges (Cyperus spp.), common water-purslane (Ludwigia palustris), and golden club (Orontium aquaticum). Common water-willow (Justicia americana) often forms dominance patches on clayey mudflats and bars. Vegetation of mucky channel edges is usually taller and contains Common threesquare, soft-stem bulrush, and square-stem spikerush (Eleocharis quadrangulata), along with pickerelweed (Pontederia cordata var. cordata), arrow-arum (Peltandra virginica), wild rice (Zizania aquatica), tidal-marsh amaranth (Amaranthus cannabinus), swamp barnyard grass (Echinochloa walteri), and other more typical marsh species.

Reference: Coulling 2002, Walton et al. 2001.

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

This link opens a new browser window to display a larger photo Narrow tidal shore community dominated common threesquare (Schoenoplectus pungens var. pungens) and dotted smartweed (Persicaria punctata), along the Potomac River at Dyke Marsh, Fairfax County (George Washington Memorial Parkway). Ice-scouring is an important environmental factor along the upper tidal Potomac , resulting in locally coarse, gravelly-cobbly shores. Photo: Kristin Taverna.

REPRESENTATIVE COMMUNITY TYPES:
Five community types have been classified through analysis of data from 30 plot samples (map), as part of a comprehensive classification of 798 Virginia and Maryland tidal plots (NatureServe in prep.). The first community type listed below is relatively robust and well supported by quantitative data. The other four communities are supported by limited plot data and observations consistent with descriptions in the USNVC. In some cases (e.g., CEGL006058 and CEGL006352), these types appear to be conceptually similar and overlapping in floristics. Additional data collection and analysis is needed to determine whether these should be merged into a broader unit. Click on any highlighted CEGL code below to view the global USNVC description provided by NatureServe Explorer.
  • Peltandra virginica - Schoenoplectus (pungens, tabernaemontani) Tidal Herbaceous Vegetation
    High-Energy Tidal River Shore (Arrow-Arum - Bulrush Mud Flat Type)
    USNVC: = CEGL006578
    Global/State Ranks: GNR/S3?

  • Schoenoplectus pungens Tidal Herbaceous Vegetation
    High-Energy Tidal River Shore (Common Threesquare / Northern Type)
    USNVC:= CEGL004188
    Global/State Ranks: GNR/S1?

  • Justicia americana Tidal Herbaceous Vegetation
    High-Energy Tidal RiverShore (Water-Willow Type)
    USNVC: = CEGL006579
    Global/State Ranks: GNR/SU

  • Isoetes riparia Tidal Herbaceous Vegetation
    High-Energy Tidal River Shore (Shore Quillwort Freshwater Type)
    USNVC: = CEGL006058
    Global/State Ranks: GNR/SU

  • Eriocaulon parkeri - Persicaria punctata Tidal Herbaceous Vegetation
    High-Energy Tidal River Shore (Parker's Pipewort Freshwater Type)
    USNVC: = CEGL006352
    Global/State Ranks: G2/SU

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