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The Natural Communities of Virginia
Classification of Ecological Community Groups

Second Approximation (Version 2.7)
Information current as of February, 2016

Table of Contents Table of Contents

Tidal Shrub Swamps

This group comprises tidally flooded and wind-tidally flooded shrublands of estuarine rivers and embayments. Tidal shrub swamps range along Atlantic and Gulf coasts from Maine to Texas. In Virginia, they represent diverse vegetation that frequently occurs in fringes or ecotones between emergent tidal wetlands and swamp forests or uplands. Examples also occur on depositional islands in large meanders of tidal rivers. Several community types have been classified, including a strictly freshwater type dominated by smooth alder (Alnus serrulata) and black willow (Salix nigra); wax myrtle (Morella cerifera) and/or Carolina willow (Salix caroliniana)-dominated shrublands of lunar-tidal and wind-tidal oligohaline systems, and a marsh-elder (Iva frutescens)-dominated shrubland of lunar-tidal, mesohaline systems. Additional shrubs of freshwater and oligohaline stands include buttonbush (Cephalanthus occidentalis), swamp rose (Rosa palustris), silky dogwood (Cornus amomum), arrow-wood (Viburnum dentatum var. dentatum), winterberry (Ilex verticillata), and poison ivy (Toxicodendron radicans var. radicans), while high-tide bush (Baccharis halimifolia) is a frequent associate of the mesohaline types. The herbaceous flora associated with tidal shrub swamps is very diverse and typically contains species characteristic of both tidal marshes and swamp forests. The ecological dynamics, state-wide distribution, and conservation status of communities in this group are poorly known.

References: Coulling (2002), Fleming and Moorhead (1998), McCoy and Fleming (2000).

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 A wind-tidal shrub swamp along Milldam Creek near its confluence with the North Landing River (North Landing River Natural Area Preserve). Wax myrtle (Morella cerifera), royal fern (Osmunda spectabilis), and sawgrass (Cladium jaimacense) are abundant species here. Photo: Gary P. Fleming / © DCR Natural Heritage.

Vegetation in this group is poorly inventoried and represented by only 22 plot samples (map). Of the four community types recognized to date, only the oligohaline type is reasonally well supported by quantitative data. However, the overall classification was based on a fairly comprehensive analysis of 181 plots from Virginia and Maryland, where this group has been extensively sampled (NatureServe, in prep.). Because of the small-patch to linear nature of these communities and their proximity to both herbaceous-dominated marshes and more structurally complex swamp forests, standard plot sampling is often difficult. Click on any highlighted CEGL code below to view the global USNVC description provided by NatureServe Explorer.
  • Alnus serrulata - Salix nigra / Pilea (fontana, pumila) Tidal Shrubland
    Freshwater Tidal Shrub Swamp
    USNVC: = CEGL006843
    Global/State Ranks: GNR/SU

  • Morella cerifera - Rosa palustris / Osmunda spectabilis - Thelypteris palustris Tidal Shrubland
    Oligohaline Tidal Shrub Swamp
    USNVC: = CEGL004656
    Global/State Ranks: G4/S3

  • Iva frutescens / Spartina cynosuroides Tidal Shrubland
    Mesohaline Tidal Shrub Swamp (Riverine Type)
    USNVC: = CEGL006847
    Global/State Ranks: GNR/SU

  • Iva frutescens / Spartina patens - Distichlis spicata Tidal Shrubland
    Mesohaline Tidal Shrub Swamp (High Salt Marsh Type)
    USNVC: = CEGL006848
    Global/State Ranks: G5/SU

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