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Site Type: Rangeland Sandy <br />MLRA: 69 -Upper Arkansas Valley Rolling Plains R069XY026CO <br />Increased Blue Grama Plant Community <br />This plant community evolves with continuous grazing. When compared to the Historic Climax Plant <br />Community; sand bluestem, yellow Indiangrass, prairie sandreed, switchgrass, and western <br />sandcherry have decreased in frequency and production. Blue grama is the dominant grass species. <br />Sand dropseed, red threeawn, hairy goldaster, Texas Croton, slimflower scurtpea, western ragweed, <br />stickleaf, heath aster, lupine, loco, milkvetch and cactus have increased. Soils that have a sandy <br />loam or coarser subsoil will show an increase in sand sagebrush. <br />Continuous spring grazing with summer deferment will reduce the cool season component <br />(needleandthread, western wheatgrass, sun sedge) of this plant community and increase the warm <br />season component. Continuous summer grazing with spring deferment will reduce the warm season <br />component (sand bluestem, yellow Indiangrass, prairie sandreed, switchgrass) of this plant <br />community and increase the cool season component. <br />The risk of losing key tall warm season grasses, important fortis and shrubs is a major concern. <br />Prescribed grazing with adequate recovery periods between grazing events will enable the land user <br />to maintain the vegetation or move it toward the HCPC. Continuous grazing will take this plant <br />community past an ecological/economic threshold resulting in costly revegetation practices or require <br />many years of prescribed grazing to reverse the process. <br />Blue grama is increasing at the expense of the tall grasses and deep-rooted shrubs. Water cycle, <br />nutrient cycle and energy flow are becoming impaired do to a shift in root structure and species <br />composition. Less litter is being produced. This is an early stage of desertification. <br />Production in this community can vary from 250 to 900 pounds of air-dry vegetation per acre per year <br />depending on weather conditions and averages 600 pounds. <br />The following is the growth curve of this plant community expected during a normal year: <br />Growth curve number: CO6905 <br />Growth curve name: Warm season dominant, cool season sub-dominant; MLRA-69; upland coarse <br />textured soils. <br />JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC <br />0 0 5 10 22 35 15 10 3 0 0 0 <br />(monthly percentages of total annual growth) <br />Transitions or pathways leading to other plant communities are as follows: <br />• Continuous orazino without adequate recovery periods between grazing events will move this <br />plant community across an ecological threshold toward the Sodbound Blue Grama without Sand <br />Bluestem, Prairie sandreed and Needleandthread Plant Community. <br />Prescribed prazinp that allows adequate recovery periods following grazing occurrences and <br />proper stocking can bring this plant community back to the Blue Grama, Prairie sandreed, Sand <br />Bluestem Plant Community (HCPC). <br />Low Plant Density, Excessive Litter Plant Community <br />This plant community occurs when grazing is removed for long periods of time in the absence of fire. <br />Most of the species occurring in the HCPC are present in this plant community but are reduced in <br />abundance and production. Much of the nutrients are tied up in excessive litter. The semiarid <br />environment and the absence of animal traffic to break down litter slow nutrient recycling. <br />Aboveground litter also limits sunlight from reaching plant crowns. Many plants, especially <br />bunchgrasses die off. Thick litter and absence of grazing or fire reduce seed germination and <br />establishment. <br />Technical Guide USDA NRCS <br />Section IiE 8 Rev. 3104 <br />