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1994 decrease was largely a decrease in the number of sagebrush; mountain snowberry • <br />remained nearly constant. The small 1995 decrease may be an artifact cf the fact that the sheer <br />bulk of herbage that constitutes an average herbaceous production of 4570 oven-dry pounds per <br />acre inevitably obscures and frustrates the most conscientious search of the ground for small <br />shrubs, especially snowberry. Of course, that bulk of overlying herbage that obscures such <br />small shrubs from view also prevents them from receiving direct sunlight, weakening them <br />incrementally. The below-ground competition between the lush herbaceous growth and shrubs <br />is likely to be fierce. These negative influences on shrubs may have caused some to die since <br />1994. With less extensive herbaceous cover present in 1996, the small increase observed may <br />be on the order of the number obscured by heavy growth in 1995. <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 (see Table 12, Shrub Density -Wadge Pasture). Random variation in <br />sample placement could affect the relative degree to which these extremes are sampled and could <br />create apparent differences that do not reflect changes in the true shrub population of the Wadge <br />Pasture. It should be noted, however, that an independent sampling of the Wadge Pasture for <br />purposes of evaluating the use of a two-stage statistical design (see below) resulted in a mean of • <br />239 stems/ac, a value well within the 90 percent confidence limits of the one-stage sampling <br />(Figure 3). <br />Two-Stage Shrub Density Sampling <br />Sample adequacy for the one-stage (normal) sampling of shrub density in the Wadge Pasture <br />was 469 samples (Table 21). This figure is typical or even relatively low for the assessment <br />of woody plant density using simple random statistical design (for example, minimum sample <br />sizes for the other reclaimed areas sampled in 1995 varied from 469 to 1942; see Table 21). <br />Evaluation of an alternative statistical approach using atwo-stage design as described by <br />Cochran (1977) was undertaken again in 1996 as it had been in 1994 and 1995 to explore <br />ways to bring achievement of an adequate sample size within range of a practical field effort. <br />In accordance with atwo-stage statistical design, the Wadge Pasture was equally divided into <br />twenty primary sample units of approximately 15 acres each (Map 2); of the twenty primary <br />units, fifteen were randomly chosen for sampling. Fifteen was chosen as a sample size that was <br />• <br />24 <br />