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,__ .._ , °~IIBIT J - 1 USDA, Soil Conservation Service Section II-E llNITED STATES DEPARTMENT OF AGRICULTURE SOIL CONSERVATION SERVICE Las An:n+as COLORADO FIELD OFFICE Gravel Hreaks 1164 ECO Site Description MLRA 69A, 69B, 67 August 1983 A.. PHYSICAL CHARACTERISTICS 1. Physiographic Features This site generally occurs as a high bench along main drainages such as Fountain Creek, Arkansas, Huerfano, Purgatoire, and Apishapa Rivers. It also frequently occurs along major tributaries to these rivers. Slopes range from 9 to 30 percent. Elevation ranges from 3,500 to 6,000 feet (1,067 to 1,825 meters). I[ occurs on all exposures. 2. Climatic Features a. The climate is semi-arid. Average annual precipitation is 10 to i3 inches (25 to 33 cm) of which 75 to 80 percent falls during the growing season. Winters are generally cold and dry. What snow that does fall generally will melt or blow off most of those areas. High intensity storms and hot dry winds in the summer are common. These result in high evapotranspiration rates. Jan Feb March April May June July Aug Sept Oct Nov Dec .36 .37 .70 1.24 1.82 1.36 1.92 1.72 .93 .78 .52 .34 b. The average annual temperature is 53° F (12° C). with a frost-free period of between I50 to 175 days. Spring growth begins between April 1 and May 1. Warm season species are generally 15 to 20 days later in green-up. Shrubs species start growth about May 5 to May 15. 3. Naive (Climax Potential) Vegetation a. The plant community on this site consists of 85 to 90 percent grasses, 5 percent (orbs and 5 to 10 percent shrubs air-dry weight. Sideoats grams dominates the site. Little bluestem, blue grams, galleta, and needleandthread are the other mayor producers on this site. Indian ricegrass, big bluestem, hairy grams, New Mexico feathergrass, sand dropseed, and red threeawn also occur in minor amounts.