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1.6 Vegetation
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<br />The Project will occupy approximately 22.7 acres of Pinyon - Juniper Vegetation
<br />Association, 23.9 acres of Sagebrush Vegetation Association, and 1.5 acres of
<br />Barren/Rock Outcrop. The Pinyon - Juniper Association in the Project area is
<br />characterized by low growing pinyon pine and Utah juniper woodlands. Overstory varies
<br />from sparse (20 to 50 percent cover) to open (50 to 80 percent cover) woodland, and
<br />understory shrub and grass -forb productivity generally varies inversely with overstory
<br />closure. The understory generally consists of Indian ricegrass, mutton bluegrass, western
<br />wheatgrass, slender wheatgrass, and needle - and - thread grass. Mountain mahogany, big
<br />sagebrush, and flowery phlox are the dominant shrubs on sites with more favorable soil
<br />and climatic conditions. Douglas rabbitbrush, antelope bitterbrush, creeping barberry,
<br />and mountain mahogany occur on sloes with rock outcrops over more than 30 percent of
<br />the area.
<br />Vegetation in the Sagebrush Vegetation Association is influenced by many interacting
<br />and interdependent ecological factors including climate, soils, topography, fire history,
<br />and grazing history. The subspecies Wyoming sagebrush is 2 to 3 feet tall and occupies
<br />loam soils on ridges; the subspecies basin big sagebrush is typically 6 to 8 feet tall,
<br />sometimes has closed overstory, and occurs in valley bottoms.
<br />The Sagebrush Association is usually an open stand of sagebrush with an understory of
<br />grasses including western wheatgrass, mutton bluegrass, cheatgrass, needle- and - thread
<br />grass, Indian ricegrass, and various sedges. Common shrubs include Douglas
<br />rabbitbrush, flowery phlox, shadsale saltbush, gray horsebrush, and winterfat.
<br />The Barren/Rock Outcrop Association includes those areas such as barren rock, rock
<br />outcrops, cliffs, and talus slopes of the dry or ephemeral drainages which feed into
<br />Yellow Creek. The vegetation of this Association is sparse but includes grasses:
<br />bluebunch wheatgrass, streambank wheatgrass, needle - and - thread grass, junegrass,
<br />Indian ricegrass, and blue grama; forbs: buckwheat, daisy, phlox, globemallow,
<br />pussytoes, and nailwort; shrubs: fringed sage and rabbitbrush.
<br />1.7 Existing Soils Information and Erosion Potential
<br />The soils on the project Area were mapped by he Soil Conservation Service (SCS and
<br />now the Natural Resource Conservation Service) in an Order III soil survey of Rio
<br />Blanco County. An Order III survey mainly delineates soil associations, complexes, and
<br />consociations with a minimum size map unit of about 6 acres. Complete detailed maps
<br />and mapping unit descriptions exist in the published survey by the SCS -1982. Soil
<br />mapping units occurring on the Project and their physical characteristics, including
<br />permeability, available water holding capacity, rate of surface runoff, and water erosion
<br />hazard, are described in Attachment 2 included with this SWMP.
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