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Even though data are scarce for other major shrub species, it is logical to extend the effects of dense <br />• oak brush stands to the other overstory species as well. Therefore a standard based upon naturally <br />occurring stem densities typical of the mine site is inappropriate. <br />In 1979, Trapper Mine Environmental staff initiated a field investigation to examine the correlation <br />between varying shrub densities and use by sheep, deer and elk. The goal was to develop a regression <br />equation which could then be used to establish a revegetation shrub density standard. Data from the <br />1979 study are presented in Table 4.4-11. The following linear regression equation was developed from <br />the density-use data collected in the fall of 1979: <br />Yi= P o + P A <br />Y = 57.89 + (-.2174)(x) <br />where: P 1= SSxy SSx = £ Xi2 - (£ Xi)2/n = 177738.63 <br />SSX <br />SSxy = £ (Xi Y) - (£ Xi)( £ Yi)/n = -38648.84 <br />SSy = £ Yi2 - (£ Yi)2/n = 16369.79 <br />P o=Y- P 1X <br />7 =31.89,X=119.58 <br />A calculated correlation coefficient (r2) for the above regression equation is -.51. For biological <br />relationships, an r2 greater than +.5 is considered acceptable. In this case, r2 denotes an inverse <br />• relationship, i.e. as stem density increases, animal use (sheep) decreases. <br />In the 1979 study, scat from three species of ungulates were inventoried within circular 10 sq. meter <br />plots. Of the three species (elk, deer and sheep) it was found that relationships of stem densities and/or <br />stem diameters when compared to total sheep pellets gave the best r2 value. <br />In order to analyze a revegetation shrub density standard for range sites A and B, the above linear <br />regression equation was used to generate Table 4.4-12. This table shows that if the stem densities that <br />existed prior to mining in range site A and B were reestablished, it would result in a decrease in the <br />potential use by livestock (sheep). The level of use would be 31.9% below the maximum attainable <br />based on the regression equation. In addition, the cost would be about $81,500 per acre if all shrubs to <br />meet this density were obtained from transplants. Therefore, Trapper Mine will establish shrub clumps at <br />no less than 1.6 acres in extent on range sites A and B. Distance between shrub clumps will not <br />generally exceed 1,400 feet. No shrubs will be seeded on range site C where the primary postmining <br />land use will be domestic grazing. <br />A determination of successful shrub revegetation will be based upon the following 3 points: <br />1) Shrub standards will not be set for range site C (big sagebrush-grass range site). Range site C is <br />primarily domestic grazing land. Any use by deer or elk is purely incidental. This type of use occurs <br />r1 <br />L J <br />4-113 <br />Revision: 112- 41 <br />Approved: z/i8?ss