Maritime Dune Grasslands
These coastal grass-dominated 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 compositional 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 beach grass (Calamagrostis breviligulata ssp. breviligulata), sea oats (Uniola paniculata), bitter seabeach grass (Panicum amarum var. amarum), beach panic grass (Panicum amarum var. amarulum), and seaside little bluestem (Schizachyrium littorale).
On steep dune slopes facing the ocean, American beach grass often forms narrow, almost monospecific stands. The crest of primary dunes and more gentle back slopes, 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), sea-beach evening-primrose (Oenothera humifusa), spurges (Euphorbia bombensis and Euphorbia polygonifolia), purple lovegrass (Eragrostis spectabilis), purple sandgrass (Triplasis purpurea var. purpurea), dune marsh-elder (Iva imbricata), and dune sandbur (Cenchrus tribuloides). Away from the primary dune and salt spray, a series of smaller secondary dunes and terraces spread inward and are characteristically colonized by various combinations of beach panic grass, saltmeadow cordgrass, and/or seaside little bluestem. This zone contains the same sparse assemblage of species as the previous zone with the addition of saltmeadow cordgrass, but with greater cover of drought-tolerant species such as purple sandgrass and dune sandbur.
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 beach 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).
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© DCR-DNH, Gary P. Fleming.