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Pubescent wheatgrass and crested wheatgrass showed the highest <br />survival of xeric species planted (8.8 and 5.7 plants/.Sm2, respective- <br />ly) (Table 3.4-3). Density for the remaining species was less than 2 <br />plants/ .5m2 is 1979. All species declined in canopy cover between Hay <br />and September, or increased only slightly. The largest cover increase <br />was recorded for yellow clover (16°,~ in ?]ay; 22.52 in September). Survi- <br />val of xeric species was more evenly distributed over all slopes and <br />aspects, indicating better adaptation by xeric species on south-facing <br />slopes than mesic mixture species. <br />In summary, density data indicate that the mesic mixture suffered <br />substantial seedling losses during the 1978 summer drought, and survi- <br />vorship was greatest on north aspects; xeric mixture species showed less <br />mortality, and better adaptation to south aspects. Canopy cover changed <br />little between years for both mixtures. Cover geaerall}• declined be- <br />tween Hay and September, a result attributed to dry summer conditions <br />and seasonal senescence. Average production in 1979 for the mesic <br />mixture increased slightly over 1978 despite substantial seedling mor- <br />tality; xeric mixture production increased approximately three times <br />• over 1978, indicating that xeric plants were increasing in size and <br />establishing well. <br />3.4.2 Statistical Comparisons <br />The following discussion is oriented around the questions that a <br />reclamation specialist might ask about the relative importance of the <br />treatments applied and the extent to which results obtained in the <br />experiment contribute answers to these questions. This discussion <br />parallels that presented in the First Annual Report (ERT 1979) to permit <br />data comparisons between years. <br />1. Effects of mulching on plant growth on north and south aspects <br />of 2:1 and 4:1 slopes (Table 3.4-4). <br />Oa 2:1 south slopes, density was aoa-significant with respect to <br />mulch applied; on 2:1 north slopes densities under both mulches (hydro- <br />mulch, excelsior) were significantly higher than the control, and densi- <br />ty was significantly higher under excelsior than hydromulch. With the <br />exception of the north .slope control, south slope density was signifi- <br />cantly lower than on the north slope. <br />28 <br />