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11 <br />conclude that the sites, 1 and 3 production sample means, are from the same popu- <br />lation. Therefore, the third site is now range site B. Further, the criteria <br />for high and low elevation was adjusted from 7,400 feet to 7,200 feet based on a <br />more exact definition of vegetative response to elevation -soil temperature <br />effects. The definition is based on a soil survey analysis which placed the <br />change in soil temperature regimes at 7,200 feet on west facing slopes and <br />slightly lower for north and east slopes. <br />Range site C has a big sagebrush -grass vegetation type that occurs along the <br />lower elevations of the proposed mine plan area. It is composed of what was <br />thought to be two range sites in 1978-1.979. This site totals 2„874jacres and is <br />composed of north, west and east slopes. A statistical analysis of 1979 produc- <br />tion data (Appendix D) (1979 range site 4 and 5) showed that the null hypothesis <br />could not be rejected at Ok =.05 (Table 2.3-10) in a comparison of sample means. <br />The combined range sites are now designated as range site C. This range site is <br />bounded on the south by mountain shrub and on the north by large broken blocks of <br />• dryland wheat fields. <br />The major uses of all three range sites are wildlife habitat and domestic live- <br />stock grazing. <br />Disturbed acreage within the proposed permit area as of 10/1/80 are displayed on <br />Map M18. Table 2.3-11 details disturbance by acre for each vegetation type based <br />on the following periods of disturbance: prior to August 3, 1977; between August <br />3, 1977, and May 3, 1978; between May 3, 1978, and January, 1981. The May 3, <br />1978 thru January, 1981 disturbed acreage assumes the permit application will be <br />approved prioir to major additional disturbance due to occur in May or June of <br />1981. <br />2.3.3 Description of Cover, Production, Shrub Density and Diversity <br />. The Mountain shrub type based on 1979 vegetation sample data has been separated <br />into two major range sites, A and B. The basis for the division into two major <br />2-97 <br />