Land use: Most of this area is in farms and ranches, but urbanization is increasing in the central and southern parts. More than 40 percent is native rangeland, and about 15 percent is improved pasture. Beef cattle are the principal livestock, but dairy cattle and sheep are important in the central and southern parts. About 25 percent of the area, including valleys, bottom lands, and the deeper soils on uplands, is cropland. Oats, wheat, grain sorghum, forage sorghum, cotton, corn, and hay are the principal crops. Native pecan orchards are common along the flood plains. Deer and wild turkey hunting leases are an important source of income in the south.
Elevation and topography: Elevation is 200 to 400 m but ranges from 400 to 500 m on some of the high peaks in the southwest and in the Arbuckle Mountains in the north. The area consists of a gently rolling to hilly, dissected limestone plateau and of the low, rugged Arbuckle Mountains. Stream valleys are shallow and narrow in their upper reaches but deepen and broaden near the eastern edge of the area. Steep slopes border the valleys of larger streams and are along the side slopes of flat-topped plateaus and in most of the Arbuckle Mountains. Relief is mainly several meters, but the large valleys are about 50 m below the adjacent uplands.
Climate: Average annual precipitation - 700 to 1,025 mm. Maximum precipitation is in spring and in fall. More than half of the precipitation falls during the frost-free period. Average annual temperature - 17 to 21 C. Average freeze-free period - 200 to 260 days.
Water: The moderate but somewhat erratic rainfall is the source of water for crops, pasture, and range. The large rivers flow all year. Several large lakes and flood-detention reservoirs are potential sources of water for irrigation but are little used for this purpose now. Deep ground water is abundant, and many springs and wells are throughout the area.
Soils: Most of the soils are Ustolls, Usterts, and Ochrepts. They are well drained and moderately well drained and moderately fine textured and fine textured. They have a thermic temperature regime, an ustic moisture regime, and montmorillonitic, mixed, or carbonatic mineralogy. Moderately deep to deep, nearly level to gently sloping Pellusterts (San Saba, Branyon, and Slidell series) and Chromusterts (Crawford and Sanger series) are on uplands, in upland valleys, and on ancient stream terraces. Shallow to moderately deep, gently sloping Calciustolls (Purves, Bolar, and Denton series) are on the smooth uplands. Very shallow to shallow, gently rolling to hilly, mostly stony or gravelly Haplustolls (Aledo and Eckrant series), Calciustolls (Tarrant, Purves, and Doss series), and Argiustolls (Speck and Tarpley series) are on limestone ridges and plateaus. Shallow, gravelly, or stony Ustochrepts (Brackett series) and Calciustolls (Real series) are on the steeper side slopes of the plateaus. Deep, well drained Haplustolls (Krum series), Argiustolls (Blanket series) and Calciustolls (Venus and Lewisville series) are on outwash in the valleys and along stream terraces. Deep, well drained Haplustolls (Frio, Bosque, and Gowen series) are on flood plains. Deep Argiustolls (Durant series), Paleudolls (Newtonia series), and Haplustalfs (Normangee series) are on smooth uplands in the north. Shallow, stony Haplustolls (Kiti series) and areas of rock outcrop occur on the Arbuckle Mountains in the north.
Potential natural vegetation: This area supports prairie vegetation with widely scattered live oak trees. Little bluestem, indiangrass, big bluestem, and switchgrass are typical species. Little bluestem, sideoats grama, tall grama, and scattered shrub live oak and juniper trees characterize the natural vegetation on the very shallow soils and along escarpments.
(From "Land Resource Regions and Major Land Resource Areas of the United States". United States Department of Agriculture Soil Conservation Service Handbook 296. Dec. 1981. pages 61-62.)