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Site Type: Rangeland <br />MLRA: 69 - Upper Arkansas Valley Rolling Plains <br />Limestone Breaks <br />R069XY058CO <br />Plant Communities <br />Ecological Dynamics of the Site: <br />Continuous grazing without allowing for adequate recovery opportunities between grazing events <br />causes this site to deteriorate. Grasses such as little bluestem, sideoats grama, big bluestem, <br />switchgrass, yellow Indiangrass, New Mexico feathergrass, western wheatgrass and needleandthread <br />decrease in both frequency and production. Blue grama, hairy grama and galleta will increase. Forbs <br />and shrubs such as purple prairie clover, American vetch, winterfat and fourwing saltbush will <br />decrease. Mid and tall grasses can eventually be removed from the plant community. Over the long- <br />term, continuous use will result in large amounts of bare ground. Species such as red threeawn, sand <br />dropseed, mat loco, sessile nailwort, small soapweed, broom snakeweed and annuals will increase or <br />invade the site. <br />Drier and warmer climatic conditions exist in the central portion of MLRA -69. This area includes the <br />eastern half of Pueblo county, northern Otero, extreme northwestern Bent, western edge of Kiowa, <br />southern edge of Lincoln and all of Crowley County. These conditions are primarily caused by a rain <br />shadow effect from the southern Rocky Mountains. Evapotranspiration rates (atmospheric demand) <br />will be higher in this area of MLRA -69. Total annual production will typically be lower. <br />The historic climax plant community (description follows the plant community diagram) has been <br />determined by study of rangeland relic areas, areas protected from excessive disturbance, seasonal <br />use pastures, short durations /time controlled grazing and historical accounts. <br />The following is a diagram that illustrates the common plant communities that can occur on the site <br />and the transition pathways (arrows) among communities. Bold lines surrounding each plant <br />community or communities represent ecological thresholds. The ecological processes will be <br />discussed in more detail in the plant community descriptions following the diagram. <br />Technical Guide <br />Section IIE <br />USDA NRCS <br />Rev. 3/04 <br />