25b. Rolling Sand Plains
Square Miles: 2661
Physiography: Sandy undulating plains with small scattered areas of active sand dunes. Few perennial streams.
Geology: Eolian sand sheets and dunes over Miocene sandstone (Ogallala Formation).
Potential Natural Vegetation: Sandsage prairie: sand sagebrush, sand bluestem, prairie sandreed, and little bluestem. This community type sometimes is called sandsage steppe due to the presence of a dominant shrub, however, sandsage prairie is the name most frequently used in the plains.
Land Use and Land Cover: Predominantly rangeland with irrigated agriculture.
25c. Moderate Relief Rangeland
Square Miles: 3084
Physiography: Irregular plains with moderate slope. Intermittent streams, with a few large perennial streams. Historically, perennial streams fed by isolated springs may have been more abundant, but water consumption for agriculture and the lowering of the watertable have reduced flow and dried up springs and many streams.
Geology: Loess mantled uplands. Sandy, gravely and loamy colluvium. Miocene sandstone (Ogallala Formation).
Potential Natural Vegetation: Combination of shortgrass and mixedgrass prairies, with mostly mixedgrass prairie in the north. Shortgrass prairie (blue grama and buffalograss) dominates on upland sites, giving way to mixedgrass prairie (little bluestem, side oats grama) on slopes, more mesic sites along rivers and streams, and also on sites overlain by thicker loess deposits. In the south, largely on Cretaceous chalks, a unique association called the chalk flat prairie, which is a mixedgrass prairie.
Land Use and Land Cover: Rangeland and some small areas of dryland farming with major crops of winter wheat and grain sorghum.
25d. Flat to Rolling Cropland
Square Miles: 17882
Physiography: Flat to rolling plains. Few streams, mostly intermittent.
Geology: Loess mantled uplands with alluvial deposits. Northern area: Sandstone and siltstone (Ogallala Formation) with thin loess mantle. Also some Brule Formation (White River Group).
Potential Natural Vegetation: Mixedgrass prairie in the north: needle and thread, blue grama, threadleaf sedge, prairie sandreed, and western wheatgrass. Shortgrass prairie to the south: blue grama, buffalograss, and scattered, isolated sites with alkali sacaton, western wheatgrass, and inland saltgrass.
Land Use and Land Cover: Dryland cropland with large areas of irrigated agriculture. Major crops include winter wheat, with corn, grain sorghum, and sugar beets grown under irrigation.
25e. Rolling Cropland and Range
Square Miles: 765
Physiography: Nearly level to rolling plains. Few streams, mostly intermittent.
Geology: Eolian deposits; thin mantle of loess, loessial alluvium, and colluvium.
Potential Natural Vegetation: Shortgrass prairie in loess mantled areas with sandsage prairie in areas with coarse textured soils.
Land Use and Land Cover: Irrigated and dryland cropland, and rangeland with a significant amount of bare ground. Major crops include winter wheat, grain sorghum, alfalfa, and corn.
Natural Areas in the Western High Plains