2009-09-21_PERMIT FILE - C1981010A (44)

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• 4.4.1.3 Shrub Density Standards Revegetation standards for shrub reestablishment at Trapper Mine should not be established from direct comparisons to reference areas or premining shrub densities. An analysis of stem density data in Section 2.3.3.3 shows that the naturally occurring density of shrubby stems is prohibitive to use by grazing ungulates. In general terms, Young et al., (1967) found that forest density and understory vegetation influenced the distribution of forage utilization in areas of study in northern Oregon. Clary el al. (1978) identified two variables, perennial grass production and ponderosa pine stem density, as being primarily responsible for the variation in the pounds of forage consumed by cattle. Cook (1966) investigated twenty-one separate variables for the effect on utilization by cattle. He identified eleven variables as having a significant effect on utilization with the density of brush being consistently in the top eight. Kufeld (1977) in his study of oak stands found that dense stands will prevent access by cattle and elk and that production of grasses and fores occurring under such stands may be suppressed. Investigations have shown that cattle prefer to forage in open areas and will avoid areas where an overstory exists (Reynolds 1962; McEwen and Dietz, 1965; George and Powell, 1979). Boyd (1970) conducted an extensive study of elk of the White River Plateau. Included in his study were the degree of utilization by elk of various densities of Gambel's oak. He concluded that elk use is inhibited at densities of thiryfive percent and that elk are physically excluded on densities exceeding fifty- 10 one percent. Boyd also indicated that mature and aged stands generally have densities that exceed the above value. In addition, overmature plants are of such height as to be out of reach to deer and elk, even during winter months. Density measurements by Boyd are essentially an indication of aerial cover. Section 2.3.1 discusses cover measurements at Trapper Mine in relation to habitat descriptions. Tables 2.3-2 and 2.3-4 illustrate in percent relative cover, shrub cover by species and cover by lifeform for the mountain shrub vegetative types. Jefferies (1965) conducted a study on Gambel's oak at the San Juan Basin Experiment Station. Jefferies major conclusion was that by thinning oak brush stands, greater forage production could be realized on oak dominated ranges. It was Jefferies opinion that lower production under oak was due to the predominance of cool season species and the high degree of shading from the oak canopy. This is corroborated by the work of Tiedeman and Schmutz (1966) who were able to increase grass production by 770 Ibs per acre by destroying an oak canopy. Kufeld (1977) found that grasses increased in abundance by forty-four percent after treating oak brush. Two years after a spraying treatment, he found that elk use had increased by seventy-three percent and deer use was up sixteen percent. While deer use seems less inhibited by high shrub density, Boyd (1970) found that when oak densities (of canopy cover) above fifty-one percent were thinned, it did not adversely affect wintering deer herds. • 4-112 Revision: T/2-_4I 2/Approved: iVA3