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~, <br />`' i, • <br />• <br />, <br />! UNITED STATES DEPARTMENT OF AGRICULTURE' <br />Soil Conservation Service Colorado <br />Technical Guide RANGE $ITE N0. 289 <br />Section II E Field Office <br />August 1975 <br />RANGE SITE DESCRIPTION <br />for _ <br />CLAYEY FOOTHILLS <br />Land Resource Area: Central Desertic Basins, Mountains, <br />and Plateaus (34) <br />Colorado and Green Rivers Plateaus (35) <br />Southern Rocky Mountains (48) <br />A. PHYSICAL CHARACTERISTICS <br />1. Physlographic Features <br />This site occupies gently sloping to rolling benchlands, footslopes, <br />fans, valleys and broad ridges. It is commonly associated with ~ <br />. ~ ~ sha1P hills. Slopes are generally between 1 and 12$ and are not ~ <br />"~, significant to plant growth. Elevation is between 5500 and 7000 feet. <br />I <br />~\ 2. Climatic Features <br />- <br />Average annual precipitation Is 12 to 16 inches, except for a few <br />small areas where it may reach 18 inches. Of this, 35 to 40$ falls <br />as snow and 40 to 45$ falls between May 1 and September 30. Sumner <br />moisture Is mostly from thundershowers in late July, August and <br />September. A dry period from May to early July is typical, and June <br />is normally the driest month. Wide yearly and monthly deviations <br />are common. The most active growth of major native plants usually <br />starts in April. It extends through most of June for some plants <br />but ends in late May for others. Many plants can again take advant- <br />age of late summer rains if in good vigor. <br />Mean annual temperatures are 45° to 48° F, with a frost-free period ~ <br />of 90 to 140 days. Annual range in temperature is from 90° to -15° -- ~,, <br />or -20° F, although higher and lower extremes are sometimes recorded. ~ ~i <br />The typical late spring and early summer dry spell puts warm-season Y ~1 <br />plants at a distinct disadvantage compared to plants that can start : , <br />earlier on stored winter moisture and spring rains. Deep storage M ti• <br />of winter moisture allows sagebrush and small trees to complete `!~ <br />strongly with shallower rooted grasses during this dry period, espec- <br />ially if other factors encourage the spread of such plants. <br /> <br />