Classification of Vegetation Communities of Maryland: First Iteration

V. HERBACEOUS VEGETATION
V.A.5.N.k. Seasonally flooded temperate or subpolar grassland
V.A.5.N.k.23. RHYNCHOSPORA SPP. - PANICUM (RIGIDULUM, VERRUCOSUM) - RHEXIA VIRGINICA SEASONALLY FLOODED HERBACEOUS ALLIANCE
Beaksedge species - (Redtop Panicgrass, Warty Panicgrass) - Virginia Meadow-beauty Seasonally Flooded Herbaceous Alliance

Concept: This alliance accommodates a variety of seasonally flooded vegetation of pondshore and lakeshore environments. It occurs primarily along the Atlantic Coastal Plain from Nova Scotia, Canada, south to Georgia, with inland stations in the central Great Lakes area, the Great Valley of Virginia, and central Tennessee. Occurrences of this alliance are usually small and are dominated predominantly by herbaceous, mostly graminoid, species. Many species are annual or short-lived perennial plants. They persist for years in the seed bank until the hydrologic conditions are right for germination. Thus, species composition of particular stands may change from year to year. In interior stations of this alliance, many of these seedbank plants are species significantly disjunct from their main range on the Atlantic Coastal Plain. There are two major vegetation zones that occur in this environment: Zone 1 is a seasonally flooded zone of sparse cover by graminoids; and Zone 2 is a saturated zone of dense graminoid cover. Some associations may include a zone dominated by taller graminoids, including Saccharum spp. or Scirpus cyperinus. These zones remain largely intact, but a succession of wet or dry years can cause them to shift slightly in location. Pondshore examples of this alliance occupy a zone around a more open pond center with a longer hydroperiod. These ponds have a pronounced seasonal fluctuation in water level, filling in the winter and drying in the summer. Abundant species in this alliance include the graminoids Calamagrostis canadensis, Carex spp., Carex scoparia, Cladium mariscoides, Eleocharis melanocarpa, Fimbristylis autumnalis, Juncus spp., Rhynchospora capitellata, Rhynchospora scirpoides, and Schoenoplectus hallii (= Scirpus hallii). Some prominent forbs include Ludwigia spp., Rhexia mariana, and Rhexia virginica. Other species that may occur are Agalinis purpurea, Dulichium arundinaceum, Eleocharis melanocarpa, Eleocharis obtusa, Eleocharis palustris (= Eleocharis smallii), Eupatorium perfoliatum, Euthamia caroliniana (= Euthamia tenuifolia), Fimbristylis autumnalis, Fuirena squarrosa, Hypericum boreale, Juncus effusus, Lobelia canbyi, Rhynchospora corniculata, Rhynchospora glomerata, Rhynchospora macrostachya, Rhynchospora perplexa, Rotala ramosior, Scirpus cyperinus, Spiraea alba, Spiraea tomentosa, Stachys hyssopifolia, Triadenum virginicum, Viola lanceolata, and Xyris difformis. Examples of this alliance from Lower New England and the North Atlantic Coast of Nova Scotia south to Delaware may be found on Coastal Plain pondshores with cobble substrates and little or no organic material accumulation; the broad margins and shorelines of shallow basins or deeper ponds on variable substrates; or on the shores of glacial outwash ponds or large lakes. In the Great Lakes, stands of this alliance are found on sandy pitted outwash plains and glacial lake plains. The level topography of these plains produces gently sloping, shallow basins with no outlets and sometimes no inlets. The water table fluctuates seasonally and yearly. It is highest in late winter and spring, and during years of high precipitation. The soils are derived mainly from sand. The sand is poor in nutrients and is acidic, with pH ranging from 4.4-7.0. These conditions inhibit microbial decomposition and considerable organic material accumulates as peat. The peat mixes with sand or forms more-or-less pure deposits. Basin shorelines typically have stretches of pure sand in areas where wave action is greatest, pure peat in protected areas, and a mixture of the two substrates in other areas. In some basins, an impermeable layer of clay develops 2-5 m below the surface. This layer may hold the local water table above the regional water table for long periods. In the South, this alliance is found in upland depression ponds of the Interior Low Plateau (Eastern Highland Rim) of Tennessee, seasonally flooded anthropogenic peatland depressions in the Great Dismal Swamp of Virginia (where it may occupy seasonally ponded depressions of anthropogenic origin, such as experimental marsh restoration clearings, burned-out peat areas, or depressional basins in powerlines), seasonally flooded upland depressions occurring on clays in the Inner Coastal Plain of southeastern Virginia, as well as Grady Ponds in Georgia and possibly some vegetation of Carolina bays. In central Tennessee examples, vegetation of this alliance may grade down into that of the V.A.5.N.k Juncus repens - Eleocharis microcarpa Seasonally Flooded Herbaceous Alliance (A.1376).

Range: This alliance is found in Wisconsin, Michigan, Indiana, Massachusetts, Rhode Island, New York, Virginia, North Carolina, South Carolina, Georgia, Alabama, Tennessee, and Kentucky. It also occurs in Canada in southern Ontario and Nova Scotia.

States/Provinces: AL? CT DE GA IN KY? MA MD MI NH? NJ NS NY ON RI SC? TN VA VT WI

TNC Ecoregions: 44:C, 45:C, 46:C, 47:?, 48:C, 53:P, 56:C, 57:C, 58:C, 59:C, 61:C, 62:C, 63:C

USFS Ecoregions: 212C:CP, 212D:CP, 212Hu:CCC, 212Hv:CCP, 212Hx:CCC, 212Ka:C??, 221Aa:CCP, 221Ab:CCP, 221Ac:CCP, 221Ad:CCP, 221Ae:CC?, 221Af:CCP, 221Ag:CCP, 221Ai:CCP, 221Al:CCP, 221Ba:CPP, 222Eb:CCC, 222Ge:CCC, 222Ja:CCC, 222Jb:CCC, 222Jc:CCC, 222Jg:CCC, 222Jh:CCC, 222Ji:CCC, 222Jj:CCC, 222Ka:CCC, 222Kb:CCC, 232Aa:CCP, 232Ac:CCC, 232Ba:CCP, 232Bq:CCC, 232Br:CCC, 232Bv:CCC, 232Cb:CCC, 232Ch:CCC, M221Ab:CCC

Federal Lands: DOD (Arnold, Fort Benning, Fort Gordon, Fort Lee); USFS (George Washington); USFWS (Great Dismal Swamp)

References: Brodowicz 1989, Faber-Langendoen et al. 1996, Keddy and Sharp 1989, Russo 1997

Authors: ECS, MP, East Identifier: A.1384

Concept: This seasonally flooded, Coastal Plain wetland occurs on the central Atlantic Coastal Plain in topographically defined basins. This vegetation occurs on the relatively higher, outer margin of the basin. The substrate is a thin organic horizon overtopping deep sandy loam. The dominant species are Saccharum giganteum, Panicum verrucosum, Dichanthelium spretum (= Panicum spretum), and Fimbristylis autumnalis. Other associates include Polygonum hydropiperoides, Panicum rigidulum, Scirpus cyperinus, Proserpinaca pectinata, Rhynchospora corniculata, Juncus repens, Rhexia virginica, Scleria reticularis, Carex striata, Woodwardia virginica, Oldenlandia uniflora, and Triadenum virginicum.

States/Provinces: MD:S?, VA?

TNC Ecoregions: 58:C

USFS Ecoregions: 232B:CC

References: Berdine and Gould 1999, Fleming et al. 2001

Authors: ECS Confidence: 1 Identifier: CEGL006609

- Maryland Vegetation Classification Subset Report V.A. Perennial graminoid vegetation

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