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<br />magnd), Brown-headed Cowbird (Molothrus ater), and House Sparrow (Passer <br />domesticus). ,,1 <br /> <br />C. Vegetation, geology, soils, and topography. Vegetation <br /> <br />"The proposed project area is located in the Blackland Prairie Biotic Province and <br />Blackland Prairie Vegetation Region of Texas (Blair 1950, Hatch et al. 1990) near a <br /> <br />transition zone of the Edwards Plateau. Historically, the flora of this region was a mixture <br />of species from the grasslands of the Great Plains and deserts to the north and west and <br />the South Texas Plains to the south. Much of the indigenous vegetation of the region has <br />been modified, primarily by the replacement of native grassland communities with <br />introduced pasture grasses and by removal of existing trees. The Blackland Prairie covers <br /> <br />approximately 11,500,000 acres of north central and south central Texas. It is <br />characterized as a true prairie with little bluestem (Schizachyrium scoparium) as a climax <br />dominate species." 1 <br /> <br />"The topography of the Blackland Prairie varies from gently rolling to hilly, with <br />elevations ranging from 300 to 800 feet above mean sea level. Annual rainfall for this <br />region ranges from 30 to 40 inches, with highest rainfall in May (Correll and Johnston <br />19ï9). Typically, upland soils are dark, calcareous shrink-swell clayey soils changing <br />gradually with depth to light marls and chalks, while bottomland soils are generally <br />reddish brown to dark gray, slightly acid to calcareous, loamy to clayey and alluvial <br />(Hatch et al. 1990)." 1 <br /> <br />"Common grassland species include little bluestem, big bluestem (Andropogon <br />Gerardi), silver bluestem (Bouteloua saccharoides), hairy grama (Bouteloua hirsuta), <br />Texas grama (Bouteloua rigidiseta), Indiangrass (Shorghastrum nutans), tall dropseed <br />(Sporobolus asper), Silveus dropseed (Sporobolus silveanus), side oats grama (Bouteloua <br />curtipendula), switchgrass (Panicum virgatum). Texas wintergrass (Stipa leucotricha), <br />buffalograss (Buchloe dactyloides), Mead's sedge (Carex meadii), little barley (Hordeum <br /> <br />City of San Marcos Blanco River Preserve, Phase I <br />ENVRlONMENT AL ASSESSMENT <br />Page 5 of 14 <br />