Maritime Dune Grasslands
These coastal graminoid communities of ocean- and bay-fronting dunes are greatly influenced by storm surge activity. Communities of this group are characterized by a few well-adapted herbaceous species and exhibit zonation that is likely related to gradients of salt spray and soil moisture. Maritime Dune Grasslands occur along the Atlantic coast of the United States from New York south to South Carolina. The dominant plants in Virginia stands are saltmeadow cordgrass (Spartina patens), American beachgrass (Ammophila breviligulata), sea oats (Uniola paniculata), bitter seabeach grass (Panicum amarum ssp. amarum), beach panic grass (Panicum amarum ssp. amarulum, = Panicum amarulum), and seaside little bluestem (Schizachyrium littorale, = Schizachyrium scoparium ssp. littorale).
On steep dune slopes facing the ocean, American beachgrass often forms narrow, almost monospecific stands. The crest of primary dunes and more gentle back slopes and terraces, however, are dominated by sea oats and/or bitter seabeach grass, with a slightly more diverse assemblage of low-cover species such as seaside goldenrod (Solidago sempervirens var. sempervirens), sea-beach evening-primrose (Oenothera humifusa), spurges (Chamaesyce bombensis and Chamaesyce polygonifolia), purple lovegrass (Eragrostis spectabilis), purple sandgrass (Triplasis purpurea), sea-coast marsh-elder (Iva imbricata), and dune sandbur (Cenchrus tribuloides). Away from the primary dune and salt spray, a series of smaller secondary dunes spread inward and are characteristically colonized by beach panic grass or seaside little bluestem. This zone contains the same sparse assemblage of species as the previous zone with the addition of saltmeadow cordgrass, which forms dense patches along terraces of the smaller dunes.
Development and coastal erosion are the major threats to dune communities. Excessive walking on dunes also reduces their stability and increases the chance of breaching during storm events. The introduced Japanese sedge (Carex kobomugi), initially planted to stabilize dune systems, has become an invasive pest on the southeastern Virginia coast.
References: Clampitt (1991), Clovis (1968), Levy (1983), The Nature Conservancy (1997).
Click on the images below to open a larger image in a separate window.
|American beachgrass (Ammophila breviligulata) and sea-oats (Uniola paniculata) on the frontal dune at Chincoteague National Wildlife Refuge, Accomack County.Gary P. Fleming / © DCR Natural Heritage.|
|Seaside little bluestem (Schizachyrium littorale) dominating secondary dunes on the Outer Banks of Dare County, North Carolina, just south of the Virginia line and False Cape State Park. Photo © Gary P. Fleming.|
|Diverse maritime grassland on the frontal dunes at Cape Henry, City of Virginia Beach (First Landing/Seashore State Park). Photo © Gary P. Fleming.|
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