Remnant Grasslands of the Fayette Prairie, Texas

Abstract

Twenty-five remnant grasslands from across the Fayette Prairie of SE Texas were sampled for species frequency and basal cover as well as selected soil and topographic properties. Polar ordination was used to elucidate stand and species patterns and plant-environmental interrelationships. Three major topo-edapho-vegetation complexes were defined. Upland clay soils (Vertisols and Mollisols) were characterized by Andropogon gerardii var. gerardil, Bouteloua curtipendula var. curtipendula and Carex microdonta. Upland sandy clay loam and clay loam soils (Alfisols) had Paspalum plicatulum, Coelorachis cylindrica and Fimbristylis puberula var. puberula as characteristic species. Schizachyrium scoparium var. frequens and Sorghastrum nutans were ubiquitous dominants or codominants in all upland communities. Panicum virgatum and Tripsacum dactyloides dominated lowland clay soils (Vertisols). The Fayette Prairie should be classified as a southern extension of the True Prairie Grassland Association. INTRODUCTION The Fayette Prairie is located in SE Texas (Fig. 1). It is isolated from the Blackland Prairie to the N and the Coastal Prairie to the S by narrow strips of Post Oak Savanna. To the E it borders on the southeastern Evergreen Forest (Braun, 1950) and to the W it grades into the South Texas Plains (Godfrey et al., 1970). It once contained approximately 1.5 million ha of native grassland (Godfrey et al., 1970), but little undisturbed vegetation remains (Johnson, 1931; Launchbaugh, 1955). No quantitative analysis of the vegetation exists for the area and, as a result, available data are insufficient to adequately describe or classify the prairie. The purpose of this study is to: (1) provide a quantitative ecological analysis of remnant vegetation and soil; (2) relate differences in vegetational composition to edaphic and topographic factors, and (3) evaluate ecological affinities and determine the appropriate classification of the prairie. STUDY AREA The Fayette Prairie is characterized by a flat to gently rolling topography. Two rivers, the Brazos and the Colorado, cross the area. Uplands were historically prairie although Quercus stellata and Q. virginiana occurred occasionally as scattered individuals or in small clumps. Lowlands were dominated by stands of hardwood forest including Q. stellata, Ulmus crassifolia, Fraxinus spp. and Carya illinoiensis. Current land use is primarily for native and tame pasture with limited cropland. Geologically, the Fayette Prairie consists of material deposited in the middle to upper Miocene (Geol. Atlas Tex., 1974). Three major formations occur: the Fleming, Oakville Sandstone and Cook Mountain (Fig. 1). The Fleming formation underlies most of the area except the western margin. Laid down in the upper Miocene, it consists of a 400-m-thick layer of calcareous silty clay sediment with some medium to coarse grained sandstone. The Oakville Sandstone is slightly older. It is found as a narrow strip on the NW side and in the S-central portion of the prairie, and consists of a