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In the Wadge Pasture, shrub densities in 1988 through 1994 were 320, 476, 408, 288, 344, <br />356, and 295 stems per acre, respectively. The apparent substantial increase in density in <br />1989 was partially lost by 1990, and, by 1991, a substantial decrease was encountered, yet in <br />1992 an increase was measured. In 1991, seedlings were encountered in the amounts of about <br />1 to 7 percent of total density in the reclaimed areas; while nowhere near 1989 levels, the <br />presence of seedlings may reflect a response to greater moisture in 1991; this may be <br />responsible for the increase in density observed in 1992 which was maintained in 1993. The <br />slight increase in 1993 was mainly accounted for in an increase in mountain snowberry of <br />approximately 30 stems per acre, and 4 stems per acre of chokecherry. The 1994 decrease <br />was largely a decrease in the number of sagebrush; mountain snowberry remained nearly <br />constant. <br />The degree to which variations in the chance placement of sample points has affected these <br />averages over the years is not known, but within the Wadge Pasture, there are areas of local <br />abundance or scarcity. Random variation in the degree to which these extremes are sampled <br />could create apparent differences that do not reflect changes in the true shrub population of the <br />Wadge Pasture. It should be noted, however, that an independent sampling of the Wadge Pasture <br />• for purposes of evaluating the use of a two-stage statistical design (see below) resulted in a <br />mean of 275 stems/ac, well within the confidence limits of the one-stage sampling (Figure 3). <br />Of additional note in the shrub density sampling results for 1994 was the presence in the 1990 <br />Reclaimed Areas of 59 stems per acre of serviceberry, 87 stems per acre of chokecherry, and 4 <br />stems per acre of bitterbrush. <br />Two-Stage Shrub Density Sampling <br />Sample adequacy for the one-stage (normal) sampling of shrub density in the Wadge Pasture <br />was 399 samples(Table 61). This figure is typical for the assessment of woody plant density <br />using simple random statistical design (for example, minimum sample sizes for the other <br />reclaimed areas sampled in 1994 varied from 211 to 762; see Table 61). Evaluation of an <br />alternative statistical approach using atwo-stage design as described by Cochran (1977) was <br />undertaken to explore ways to bring achievement of an adequate sample size within range of a <br />practical field effort. <br />. 31 <br />