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<br />Management Situation by Revision Topic <br /> <br />The sections which occur on the RGNF are described below: <br /> <br />.':.: <br /> <br />3311 <br />Rio Grande Basin Section <br /> <br />Geomorphic Processll.andforms -- Nearly level to gently sloping old valley fill. Gently sloping to <br />steep hills underlain by basalt are common in the south. local relief is slight, except in the south <br />where it can be 100 meters (m). <br /> <br />lithologylStratigraphy -- Terrestrial basin fill of late Tertiary and Quaternary age. <br /> <br /> <br />Soil Taxa -- Frigid Ardisols and Entisols. Frigid Argids. <br /> <br />~: <br /> <br />Potential Natural Vegetation -- Desert shrub-grassland. Saltbush-greasewood and wheatgrass- <br />needlegrass. <br /> <br />Elevation -- 6,900 to 8,860 ft. (2,100 to 2,700 m) Precipitation -- 6 to 20 in. (15-50 em). <br />Temperature -- 38 to 50'F (4 to 10'C). Growing Season -- 100 to 140 days. <br /> <br />Surface Water Characteristics -- The Rio Grande River and small reservoirs on intermittent streams <br />provide irrigation water. The Conejos River flows through here. Wells tap into deep valley fill. <br />Salinity is a problem in much of the area. <br /> <br />Disturbance Regimes -- About 50 percent of the area is federally owned and about 50 percent is <br />in farms and ranches. About 25 percent of the area is irrigated. Some grazing on native range- <br />land in summer months. Great Sand Dunes National Monument is here. <br /> <br />. M331F <br />Southern Paries and Ranges Section <br /> <br />Geomorphic ProcesslLandforms -- Strongly sloping to precipitous mountains dissected by many <br />narrow stream valleys with steep gradients. High plateaus and steep-walled canyons are <br />common, especially in the west. Rugged hills and low mountains occurring in narrow bands <br />along the eastern slopes of the Rockies. These are strongly dissected and in many places are <br />crossed by large streams-flowing eastward from the Rockies. <br /> <br />lithologylStratigraphy -- lower Tertiary: Oligocene, Ecocene, and Paleocene. Upper Paleozoic: <br />Permian, Pennsylvanian, and Mississippian. lower Paleozoic: Permian, Pennsylvanian, and <br />Mississippian. Precambrian: Volcanic rock of the Quaternary and Tertiary periods, and <br />metamorphic and plutonic rock of the middle-Precambrian age. <br /> <br />Soil Taxa -- Mesic, frigid, and cycic Boralfs, Mesic, and frigid Ustolls and Borolls. <br /> <br />Potential Natural Vegetation -- Forests on upper slopes, alpine tundra above timberline, shrub- <br />grass and grass at lower elevations. Western sprucelfir, Douglas-fir, pineJDouglas-fir, <br />southwestern sprucelfir, alpine meadows of bentgrass, sedge, fescue,bluegrass. <br /> <br />Elevation -- 5,575 to 14,110 ft. (1,700 to 4,300 m). Precipitation - 5 to 30 in. (13 to 75 cm). <br />Temperature -- 32 to 50'F (0 to 10'C). Growing Season -- <70 to 160 days. <br /> <br />111-5 <br /> <br />\ - ,"' ...... <br />t.!.''::;'..1.L>J <br />