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.1. PANICUM VIRGATUM SEASONALLY FLOODED HERBACEOUS ALLIANCE
Switchgrass Seasonally Flooded Herbaceous Alliance

Concept: This alliance encompasses seasonally flooded areas dominated by Panicum virgatum. Most examples are maritime-related, including interdunal depressions, but associations are also described from areas in Arkansas and other interior states where streams cross prairies and natural depressions in prairies. Associated species in the maritime examples include Spartina patens, Juncus canadensis, Solidago sempervirens, Festuca rubra, Eleocharis palustris, Toxicodendron radicans, Linum medium, Carex albolutescens, and Euthamia caroliniana (= Euthamia tenuifolia). This community is variable in its expression but is typically dominated by 40-85% cover of Panicum virgatum and occurs in larger interdunal depressions (up to 0.5 hectare). Variability occurs in the cover of Panicum virgatum and the richness of associated species. In some Coastal Plain cases, Morella cerifera (= Myrica cerifera) or Baccharis halimifolia will constitute less than 10% shrub cover. The vegetation is similar in total floristic composition to Morella-dominated shrublands, but shrubs are generally lacking or at very low cover and grasses are much more abundant. In most cases, shrub coverage is much less or none and other herbs codominate. When Panicum virgatum is not as dense, it is most often associated with Schoenoplectus pungens (= Scirpus pungens), Spartina patens, or a mixture of both. Soils are characterized by a shallow organic layer (usually a few centimeters in depth) overlying loamy sand or sand. The water table is at or close to the surface in the spring. These depressions are saturated or seasonally flooded and somewhat poorly drained. Many other associations remain to be described in this alliance, and its complete range of variation described.

Range: This alliance is found in Arkansas, Kentucky, Delaware, Maryland, New Jersey, New York, and possibly in North Carolina (?), Oklahoma (?), Tennessee (?), and Virginia (?).

States/Provinces: AR CT DE KY LA MD NC NJ OK? TN? VA

TNC Ecoregions: 32:C, 39:?, 40:P, 41:C, 42:C, 43:?, 44:?, 50:P, 56:P, 57:?, 58:C, 62:C

USFS Ecoregions: 222:?, 231Da:CP?, 231Dc:CP?, 231Eb:C??, 231Ga:CC?, 231Gb:CC?, 231Gc:CCC, 232Aa:CCC, 232Ad:CC?, 232Bt:CCC, 232Bz:CCC, 232Cb:C??, 232Ch:C??, 232Ci:C??, 234Ae:CCC, M231Aa:???, M231Ab:???, M231Ac:???, M231Ad:???

Federal Lands: DOD (Arnold?, Fort Chaffee); NPS (Assateague Island); USFWS (Felsenthal)

Synonymy: P5A4aI2a. Panicum virgatum (Foti et al. 1994); Fresh marsh community, in part (Hill 1986); mesic shrub community, in part (Higgins et al. 1971); Freshwater marsh, in part (Fender 1937); Panicum virgatum Wetland Association, in part (Heckscher et al. 1995)

References: Campbell pers. comm., Fender 1937, Foti et al. 1994, Heckscher et al. 1995, Higgins et al. 1971, Hill 1986, Sneddon et al. 1996, Zollner pers. comm.

Authors: ECS, JT, East Identifier: A.1362

Concept: This medium-tall grassland association occurs in seasonally flooded basins, or interdunal swales, landward of maritime backdunes along the mid-Atlantic coast. The water table is at or close to the surface in the spring. Freshwater maintains these depressions as saturated or seasonally flooded and somewhat poorly drained. The community is generally strongly dominated by Panicum virgatum but can be variable in its expression. Associated species include Spartina patens, Juncus canadensis, Solidago sempervirens, Eleocharis palustris, Toxicodendron radicans, Linum medium, Carex longii, and Euthamia caroliniana (= Euthamia tenuifolia). This community is typically dominated by 40-85% cover of Panicum virgatum and occurs in larger interdunal depressions (up to one-half hectare). Variability occurs in the cover of Panicum virgatum and the richness of associated species. When Panicum virgatum is not as dense, it is most often associated with an even mixture of Schoenoplectus pungens (= Scirpus pungens) or Spartina patens. In some cases, Morella cerifera (= Myrica cerifera) or Baccharis halimifolia will constitute less than 10% shrub cover, but shrub coverage is usually much less or none, and other herbs codominate. Soils are characterized by a shallow organic layer (usually a few centimeters in depth) overlying loamy sand or sand. The range of this vegetation is poorly known due to the low confidence of the classification. The vegetation is similar in total floristic composition to Morella cerifera - Vaccinium corymbosum Shrubland (CEGL003906), but shrubs are generally lacking or at very low cover, and grasses are much more abundant. The community apparently occurs in New Jersey, Delaware, Maryland, and may extend to North Carolina, but the full range will require further study.

Comments: This association is very similar floristically to Panicum virgatum - Spartina patens Herbaceous Vegetation (CEGL006150); more data are needed.

Range: The community apparently occurs in New Jersey, Delaware, Maryland, and may extend to North Carolina, but the full range will require further study.

States/Provinces: CT:S?, DE:S?, MD:S?, NC:S2?, NJ:S?, VA:S?

TNC Ecoregions: 57:?, 58:C, 62:C

USFS Ecoregions: 232Aa:CCC, 232Bt:CCC, 232Bz:CCC, 232Ci:C??

Federal Lands: NPS (Assateague Island)

Synonymy: Fresh marsh community (Hill 1986) B. in part, Mesic shrub community (Higgins et al. 1971) B. in part, Freshwater marsh (Fender 1937) B. in part, Panicum virgatum Wetland Association (Heckscher et al. 1995) B. in part, Maritime Wet Grassland (Switchgrass Subtype) (Schafale 2000)

References: Berdine 1998, Bowman 2000, Breden et al. 2001, Fender 1937, Fleming 2001, Fleming et al. 2001, Heckscher et al. 1995, Higgins et al. 1971, Hill 1986, Metzler and Barrett 2001, Schafale 2000, Schafale and Weakley 1990, Sneddon et al. 1996

Authors: ECS Confidence: 3 Identifier: CEGL004129

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

View Next Topic