2011-09-19_REVISION - M1982155 (17)

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Vegetation Information EXHIBIT J Introduction The vegetation of this small site is composed of two primary, but highly related units of grassland. A minor third unit is found in and along drainageways that includes a single species of shrub. No trees are present on the site. For the most part, only one species dominates all of the vegetation, blue grama grass. The vegetation is illustrated on Exhibit C -3, Vegetation Map. Upland Grassland Unit This unit occurs on the more level portions of the proposed amendment area. In many places, cover approaches 100 percent, but on the average coverage is about 80 percent. The dominant species is blue grama, often forming a dense mat that is indicative of past overgrazing impacts. Mixed with the grama dominated grassland are a number of other species that also indicate former intensive grazing impact. These include purple three -awn, prickly pear, yucca, and cane or tree cholla. A few other ball cactus are also present along with some sages. Many of these species are strongly associated with a clay loam or silt loam topsoil which seems to cover most of the flatter topography on the site. However, in areas the soil grades quickly into a coarse gravelly and sandy soil a short distance under the surface which tends to favor an abundance of yucca. The condition of the grassland, in spite of species distribution indicating former overgrazing, is fairly good and productivity is relatively high in good years. Recent years, however, have been poor with strong to intense drought. Many yuccas are found that appear to be shedding leaves or dying and the prickly pear is often desiccated. The grasses, however, with their deep, spreading root systems have fared much better. Slope Grassland Unit Once the slope steepens from the nearly level uplands to the slopes that lead down into the wide valley to the south, the vegetation abruptly changes its character. Although most of the same species are present, density and species balance changes considerably. Most notable is a rapid decline in the cover and density. Although some areas still exhibit fairly good cover (50 to 70 percent), these are mainly confined to steeper north facing slopes in the many drainageways that lead from the level upland into the valley. In contrast, south facing slopes may be nearly bare or have a cover of no more than 25 percent. On the whole, the vegetation cover averages about 30 to 40 percent, but many isolated areas often have cover that is less than 20 percent. The primary cause of this abrupt change in the character of the vegetation is due to a major change in the soil attributes. As the level upland reaches the erosion front at the edge of the valley and the slope begins to steepen, the vegetation changes very little. However, once the bottom of the silty to clayey top layer of the flat areas is reached, the soil exhibits a very abrupt change to a rocky, gravelly texture. This is simply the exposure of the underlying gravel deposit Fountain Pit M- 1982 -155 DRMS 112 Permit Amendment Page 22