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NWRC Coastal Prairie Research Program

Community Characterizations

Both restoration and habitat management depend fundamentally on a characterization of the composition and dynamics of the vegetative communities. Only through knowing the characteristics of the native assemblages, as well as their dynamics through time, can we gain insights into restoration and management targets and the nature of responses to management activities. For these reasons, one objective of the USGS program dealing with coastal ecosystems seeks to provide adequate characterizations of native plant communities. Here we provide a synopsis of two such studies.

Vegetation Associations in a Rare Community Type - Coastal Tallgrass Prairie

Abstract: The coastal prairie ecoregion is located along the northwestern coastal plain of the Gulf of Mexico in North America. Because of agricultural and urban development, less than 1% of the original 3.4 million ha of this ecosystem type remains in native condition, making it one of the most endangered ecosystems in North America. The objective of this study was to characterize the vegetation and environmental relationships in a relatively pristine example of lowland coastal prairie in order to provide information for use in conservation and restoration. The study area was a small, isolated prairie located near the southern boundary of the coastal prairie region. Samples were taken along three parallel transects that spanned the prairie. Parameters measured included species composition, elevation, soil characteristics, indications of recent disturbance, above-ground biomass, and light penetration through the plant canopy. Fifty-four species were found in the 107 0.25-m2 plots and a total of 96 species were found at the site. Only two non-native species occurred in sample plots, both of which were uncommon. Cluster analysis was used to identify six vegetation groups, which were primarily dominated by members of the Poaceae or Asteraceae. A conspicuous, natural edaphic feature of the prairie was the presence of mounds, which are raised areas approximately 0.5 to 1 m high and 5 to 10 m across. Indicator species analysis revealed a significant number of species that were largely restricted to mounds and these were predominately upland and colonizing species. Ordination was performed using nonmetric, multidimensional scaling. The dominant environmental influence on species composition was found to be elevation and a host of correlated factors including those associated with soil organic content. A secondary group of factors, consisting primarily of soil cations, was found to explain additional variance among plots. Overall, this prairie was found to contain plant associations that are now rare in the surrounding landscape. Within the prairie, plant groups were largely separated by a suite of environmental conditions associated with topography. These results suggest that conservation and restoration efforts will need to carefully consider local topographic influences in order to be successful.

Grace, J.B., L. Allain, and C. Allen. 2000. Vegetation associations in a rare community type- coastal tallgrass prairie. Plant Ecology 147:105-115.

Vascular Flora of the Cajun Prairie of Southwestern Louisiana

Abstract: Cajun Prairie is a Coastal Prairie developed in southwestern Louisiana between the Atchafalaya and Sabine rivers where most of the European settlers were Cajuns (French Acadians).  This prairie occurs in a n area with 125 cm (50 in) of annual rainfall; possible explanations for its development in this region include a hard claypan below the surface and frequent fires.  Most of the original 1,000,000 ha of prairie have been destroyed with only a few remnants railroad strips (200 ha) remaining; this flora is based on the species observed in the remnant strips in Acadia, Allen, and Jefferson Davis parishes over a twelve year period (1987-1999).  The vascular flora includes 512 taxa in 92 families and 277 genera.  The family with the most taxa is the Asteraceae (80), followed by the Poaceae (78), Cyperaceae (50), Abaceae (35), Lamiaceae (19), Scrophulariaceae (18), and Onagraceae (14).  Some common Asteraceae taxa include Arnoglossum plantagineum, Rudbeckia hirta, R. grandiflora, Silphium gracile, S. lacinatum, Solidago odora, and several species of Liatris and Symphotrychum.  Some common and conspicuous grass (Poaceae) species include Andropogon gerardii, Panicum virgatum, Schizachyrium scoparium, Sorghastrum nutans, and Tripsacum dactyloides.  Other notable species include several species of Baptisia, Dalea candida, Eryngium yuccafolium, Euphorbia corollata, Hedyotis nigricans, and Tephrosia onobrychoides.

Allen, C.M, M. Vidrine, B. Borsari and L. Allain.  Vascular Flora of the Cajun Prairie of Southwestern Louisiana.  Proc. 17th N.A. Prairie Conference: 35-41, 2001.

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