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Site Type: Rangeland <br />MLRA: 69 - Upper Arkansas Valley Rolling Plains <br />Loamy <br />R069XY006CO <br />Plant Communities <br />Ecological Dynamics of the Site: <br />Deterioration of this site, due to continuous grazing without adequate recovery periods following each <br />grazing occurrence, will cause blue grama, buffalograss, galleta and broom snakeweed to increase. <br />Blue grama and /or buffalograss may eventually form a sod. Cool season grasses such as green <br />needlegrass and western wheatgrass will decrease in frequency and production as well as key shrubs <br />such as fourwing saltbush and winterfat. American vetch and other highly palatable forbs will <br />decrease. Red threeawn, annuals and bare ground increases under heavy continuous grazing, <br />excessive defoliation, or long -term non -use. Much of this ecological site has been tilled and used for <br />crop production. <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 duration) /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 />4 <br />USDA NRCS <br />Rev. 3/04 <br />