REP16255 - Laserfiche WebLink

Home Browse Search

On the other hand, through 1996, the heavy woody cover of the Mountain Brush Reference Area • has shown a tendency to react with delay; reduction in cover percent during drought has been delayed, as has recovery following cessation of drought. The Mountain Brush Reference Area dropped only 9.7 percentage points from 1987 to 1989 (during the woirst of the drought), but continued to drop another 2 percentage points in 1990 (as the drought +abated). In 1991, the Mountain Brush Reference Area cover increased by nearly 8 percent, and in 1992 the total cover decreased by 13 percent. The 1992 decline relates partly to the fact that the boundaries of the reference area as sarnpled for 1992 had been adjusted to reflect the originally identified reference area limits more correctly, and included less of the very heavy oak and serviceberry stands on the steep east-facing slopes; this is responsible for at least some of the decline in cover since experience has shown the dense overhead canopy of these species generally corresponds to higher total plant cover than any other type of vegetation in the area. In 1993, with the same sample area boundaries used in 1992, the total cover increased by 7.3 percent. In 1994, the Mountain Brush Reference Area was subject not only to the severe drought conditions, but was inadvertently affected by herbicide drift as a Local n3ncher attempted to remove shrub cover from nearby grazing areas. Between the drought and herbicide accident, the result was a decrease in cover to 66.8 percent; the previous lowest observed cover in the area since 1987 was 74.9 percent in 1992. What part of this decreases was attributable to • drought and what part was due to herbicide effects is not known. In the only reclaimed area measured every year (Wadge Pasture), there was a 16.5 percent drop in cover in 1994, suggesting that the drought effect may be substantial. Mountain Brush Reference cover in 1995 ~ recovered to 79.0 percent, well within the previously observed range of values. The delayed reaction of the Mountain Brush Reference Area was again shown in 1996 as cover rose following the very favorable 1995 season while all other areas declined. Herbaceous Production Only the herbaceous component was sampled for annual production in both the reclaimed and reference areas. Because the reference areas are both dominated by woody plants, the herbaceous component of production is small and is greatly exceeded by the production of the reclaimed areas where woody plants comprise only a small amount of fetal vegetation composition (Figure 2). Whether or not the large annual herbaceous production of the reclaimed areas equals or exceeds the total (woody plus herbaceous) annual production of the reference areas is unknown. f. J fs