-Little bluestem (Schizachyrium scoparium), brownseed paspalum (Paspalum plicatulum), and Indiangrass (Sorghastrum nutans) dominate remnant upland grasslands of the Upper Coastal Prairie of Texas. Lowlands are dominated by eastern gammagrass (Tripsacum dactyloides) and switchgrass (Panicum virgatum). Composition and flora of uplands are similar to those of communities over loamy Alfisols of the Fayette Prairie, a southern outlier of the Blackland Prairie. Coastal Prairie lowlands are also similar to lowlands of the Fayette Prairie. Fayette Prairie communities over Alfisols show less similarity to Fayette Prairie communities over clayey Vertisols than to Upper Coastal communities over both soil types. Therefore, the Upper Coastal Prairie should be considered part of a north-south continuum of tall grass communities within Texas. Decreased importance of big bluestem (Andropogon gerardii) and sideoats grama (Bouteloua curtipendula) and an increased importance of brownseed paspalum in the uplands represent the most significant differences in dominance relationships between Upper Coastal Prairie remnants and remnants over Vertisols within the Fayette Prairie. This shift in dominance relationships may be the result of decreased precipitation inland coupled with variation in soil type. The Coastal Prairie in Texas can be divided into two sections based on variation in soils and climate. The Lower Coastal Prairie south of the San Antonio River occurs over hyperthermic soils and is in a dry sub-humid to semi-arid moisture region, while the Upper Coastal Prairie occurs over thermic soils and is in a wet sub-humid to humid moisture region (Thornthwaite, 1948; Soil Survey Staff, 1975). Smith (1899), Bray (1906), and Tharp (1926) provided qualitative vegetation descriptions of the entire Coastal Prairie, but no comprehensive quantitative studies exist for remnant grasslands of either the Lower or Upper Coastal Prairie. It is estimated that less than 1% of an original 8 million ha of native grasslands of the entire Coastal Prairie remains in a relatively pristine state (Smeins et al., in press). Extensive surveys of the Coastal Prairie revealed that little relict grassland vegetation exists in the Lower Coastal Prairie, while the Upper Coastal Prairie contained only approximately thirty relict stands. The purpose of this study was to: 1) quantitatively document characteristics of remnant grasslands of the Upper Coastal Prairie, 2) relate vegetation to edaphic and topographic variables, and 3) compare the composition and floristics of these remnants to the Fayette Prairie, which is located to the north and is considered a southern outlier of the Blackland Prairie (Fig. 1). This comparison will elucidate the degree of relationship between the Upper Coastal Prairie and other Texas Prairies (Collins et al., 1975; Diamond, 1980; Smeins and Diamond, 1983). STUDY AREA.-The Upper Coastal Prairie in Texas comprises a narrow strip approximately 50 to 100 km wide from the Louisiana border to the San Antonio River (Godfrey et al., 1973; Smeins SOUTHWESTERN NATURALIST 29(3):321-334 A GUST 28, 1984 This content downloaded from 157.55.39.102 on Sat, 24 Dec 2016 05:12:17 UTC All use subject to http://about.jstor.org/terms The Southwestern Naturalist