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Vegetation Information <br />• <br />in the bottom of the valleys, except that the vegetation is characterized by species that preft:r dry, rocky <br />soils rather than moist, loamy soils. <br />Soil/Plant Relationships: In most areas the Tohnan series supports this vegetation. Rock outcrops <br />are also fairly common. These soils aze typically poor, thin, and infertile. Nevertheless, the vegetation is <br />often amazingly dense for a steep south facing slope. Examining the species present over rr.ost of the land <br />where these soils exist, it is quickly apparent that drought adaptation is in common to nearly all the <br />species. The fairly high density, however, is probably not a function of soil fertility so much as available <br />moisture during the critical growth periods of the year. <br />The bench environment created by quarrying will probably be rather similar to these south facing <br />slopes. The natural combination of soil and species appears to indicate that on this site, revegetation <br />species selection may be critical to the success of the revegetation. Although moisture may be limiting on <br />the bench environment and soils will exhibit low fertility, a proper selection of revegetatior. species that <br />capitalize on available moisture during critical times may result in high success in revegeta~:ion. On the <br />other hand, selecting species that do not capitalize on this interesting pattern may result in :.ow success. in <br />conclusion, the revegetation plan should carefully take into account the ecology of these south facing <br />slopes. Although the natural vegetation of the north facing slopes need to be considered, that environment <br />is unlikely to be abundant in the revegetation environment. Designing azound that environment would <br />probably be unwise and could produce disappointing results based on unrealistic expectations. <br />Cover Characteristics: Cover on the south facing slopes averages about the same as the cover on <br />the north facing slopes, that is, about 80%. However, here at least 95% of the total cover is. composed of <br />grasses and shrubs with the remaining 5% composed of trees. in a sense, the vegetation here shows a <br />reversed pattern from the north facing slopes. Less than about 2% of the total surface area is composed of <br />rock outcrops or scree. Where the slope is steeper than average, vegetation cover declines to about 40% to <br />50%, but when such areas change to slightly more gradual (and perhaps more stable) slopes, the cover <br />quickly increases back toward the average. The highest cover is seen where shrub growth is dense. There <br />is still sufficient light and warmth to support good ground cover under the shrubs. Moistun; competition <br />with shrubs is apparently low. This may be due to layering and zonation of the two different growth forms <br />with respect to their root zone. <br />Where trees dominate the local micrcenvironment, ground cover quickly declines to l0% or less. This <br />is probably due to a combination of several factors including shade, root competition for limited moisture, <br />and allelopathy~, especially near Junipers. <br />to//e/oparhy is a process where certain chemicals secreted by a plant retards the growth of adjacent plans or prevents <br />seed germination of competitors. It is a common desert plant strategy that helps limit competition where moisture is severely <br />limiting. <br />Menzer Quarry Amendment Exhibit J Page 5 <br />