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LJ <br />Appendix B Revised 9/16/82 <br />meter each accounted for 20 percent of the total biomass.. <br />T-tests were used to compare cover and productivity data in <br />the reference and affected areas. Ideally, reference and <br />affected areas should be similar for evaluation of future <br />reclamation efforts. However, several factois operate to <br />confound the data. First, natural variability within a <br />particular vegetation type and the high level of statistical <br />confidence necessary to meet the stringent requirements of sample <br />adequacy, make it likely that significant differences will <br />occur. This is amplified if the mean values are small. <br />Secondly, location of the reference area is restricted to <br />unaffected areas within the mine permit boundaries. It is, <br />therefore, difficult to locate areas which precisely represent <br />the affected areas. <br />There was only one area suitable as a reference area for the <br />dry grassland type. There was a significant difference between <br />• the reference and affected areas for both cover and productivity <br />data for the dry grassland vegetation type. Total vegetative <br />cover was 8.9 percent in the affected area and 13.5 percent in <br />the reference area. Total production was 14.22 grams per square <br />meter in the affected area and 20.42 grams per square meter in <br />the reference area. Walden Coal Company is willing to accept the <br />increased cover and productivity of the grassland reference area <br />as the standard to be applied to future revegetation success <br />determinations. <br /> <br />Sagebrush Type. The big sagebrush community <br />characteristically occurs on sites which are somewhat more moist <br />than the dry grassland type (Figure 1). Big sagebrush shrublands <br />vary widely ranging from alkaline lowlands where greasewood <br />16 <br />