Name:
NY Heritage: Brackish interdunal swales
Reference:
Ecological Communities of New York, 2nd Ed.
Description:
Temporarily tidally flooded temperate marshes in interdunal swales dominated by halophytic graminoids. Individual swales occur as small patches positioned between fore-, primary and secondary dunes in a maritime dunes system, typically on barrier islands. Swales experience dynamic fluctuations in water levels and salinity. Water levels are highest after infrequent and sporadic overwash that occurs when tides or waves overtop the berm, transporting water and suspended sand through the foredune into low-lying areas within the dune system, usually during spring tides, full moons or major storms. Flood frequency can vary from several times per year to as little as once every 25 years. At this time groundwater levels rise, vegetation may float, and water pools into temporary ponds. During the driest times, ponds evaporate, surface sands are no longer saturated, salt concentrates then enters the groundwater, and salt deposits form on the surface. Salinity is typically mixohaline, water being derived from a mix of saline ocean overwash and freshwater groundwater lens. However, it can vary greatly at certain times of the year from oligohaline (0 ppt) to supersaline (70 ppt) in response to the salinity of the groundwater and accumulation of salt during evaporation.
The dominant flora are mostly grasses, sedges and rushes including salt-meadowgrass (Spartina patens), dwarf spikerush (Eleocharis parvula), three-square (Scirpus pungens), flatsedge (Cyperus polystachyos), and jointed rush (Juncus articulatus). The abundance of any one dominant can vary widely year to year in response to salinity fluctuations. Other characteristic flora includes halophytes such as salt-meadow grass (Diplachne maritima), seaside bulrush (Scirpus maritimus), toad-rush (Juncus ambiguus), sedge-rush (Juncus scirpoides), mock bishop's-weed (Ptilimnium capillaceum), golden dock (Rumex maritimus), saltmarsh aster (Aster subulatus), red pigweed (Chenopodium rubrum), saltmarsh fleabane (Pluchea odorata), rose-mallow (Hibiscus moscheutos), knotweed (Polygonum ramosissimum), and saltmarsh-elder (Iva frutescens). Seabeach amaranth (Amaranthus pumilus) is a characteristic plant at the upper edge of the community in drift lines. Reedgrass (Phragmites australis) is questionably native in this community.
The community is known for its importance to wildlife. Characteristic fauna include piping plovers (Charadrius melodus), American oyster catchers (Haematopus palliatus), yellowlegs (Tringa melanolueca and T. flavipes), and Canada geese (Branta canadensis) (which use the community as a foraging ground), abundant salt marsh mosquitoes (Aedes spp.), fiddler crabs (Uca spp.), odonates and other insects. Eastern mud turtle (Kinosternon subrubrum subrubrum), and eastern spadefoot toad (Scaphiopus holbrookii holbrookii) reportedly use this habitat (US ACE 1995, 1999).
Soils are deep sands, often become anaerobic but lack peat accumulation. The surface is often rusty colored from a coating of blue-green algae. Community variants include semi-permanent pools, long-lived wet swales with perennial graminoids and newly-formed sparsely-vegetated damp swales with early successional annual forbs. Occurrences of this community are sometimes ephemeral representing the early stages of salt marsh or coastal salt pond formation or rapidly transforming into reed grass marshes.
Accession Code:
VB.CC.28529.NYHERITAGEBRACK
Plot-observations of this Community Concept:
7
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