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• • Vegetation Information about 1 % or 2% ground cover under the trees, and the remainder occupied by scattered shrubs. Although about 90% of the ground surface is essentially bare in most places, erosion is slight. This is mainly due to the highly organic soil that can absorb large amounts of water without eroding. South Facing Slopes: Map Unit Name: Pinon Pine/Juniper/Mountain Mahogany General Description: Tn striking contrast to the north facing slopes, the south facittg slopes are more like a desert grassland. The slopes aze generally steep and rocky and occupied by species that are typically very drought resistant. Cactus (Prickly Pear and various "pincushion" cacti) are ccmmon and in places form dense growths. Grasses are often abundant, except where the soil is very rocky. Most of the vegetation cover is composed of grasses, fortis, and shrubs. Trees form a very minor component of the vegetation and are often widely spaced or completely absent from large areas. This vegetation, although characterized and visually dominated by trees and shrubs, would actually be called a shrubby grassland, if numerical relationships are used to name the vegetation. Species diversity is very high, in fact, most of the species found over the entire site are found on these south facing slopes rather than the north facing slopes. The high species diversity is probably due to the extremely high degree of microem~ironmental diversity on the south facing slopes. In the shade of large rocks, rich growths of grass and even ferns can be found. Yet, a few feet away, in an open, hot, dry site the vegetation may be dominated by stands of Prickly Pear cactus mixed with Blue Grama and Western Wheatgrass, two typical prairie grasses. This prairie type growth may then abruptly transition into a shrub dominated vegetation composed, usually, of Mountain Mahogany. Occasionally blended with the Mountain Mahogany may be Gambel Oak, Antelope Bitterbrush, Skunkbush, or Gooseberry. The trees on these slopes are mostly Pinon Pine or Rocky Mountain Juniper, but occasional specimens of One-seed Juniper can also be found. Near the crest of the slopes and occasionally in the mid-slope area, Ponderosa Pine can also be found. Most of the trees are isolated from each other with separations (crown edge to crown edge) of 50 to 100 or more feet. The space between the trees is occupied by the high diversity grass, shrub, and forb communities. Whete the north facing slope and south facing slope vegetation units meet in the bottom of the valleys, the transition is usually very narrow. The Douglas Fir may extend a short distance (10 to 2~) feet in elevation) up the south facing slope and Juniper and sometimes Pinon may extend a similar distance up the notth facing slope. Ground cover in these transition areas is often nearly 100% and composed mainly of Bluegrass (Poa), Bromegrass (Bromus), and other species common to more moist land neaz ephemeral streams. These transition areas may also include Rocky Mountain Maple and River Alder, lwt the latter two species aze only common locally. Chokecherry can be found in the valley bottoms and growing a short distance up adjacent slopes. As mentioned previously, the slope crests where the south facing and the north facing vegetation meet is characterized by a mixture of Ponderosa Pine, Douglas Fir, Gambel Oak, and a blend of various ground level species common to each of the vegetation units. This transition is similar in structure to the transition Menzer Quarry Amendment Exhibit J Page 4