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3.3.3 Discussion and Summary <br />In 1978 it was concluded that in general the excelsior mulch treat- <br />. went caused higher near-surface temperatures than the other mulches and <br />the control on the warmer south aspect, and that excelsior application <br />resulted in lower near-surface temperatures on the cooler north aspect. <br />In 1979, it was observed that the stray treatment was cooler than excel- <br />sior on north 4:1 aspects; in contrast, excelsior was cooler near the <br />surface than straw oa south 4:1 aspects. On 2:1 north treatments, there <br />was little difference between mulches and the control; on the south <br />slope excelsior was warmer than hydromulch but cooler than the control <br />at 5cm. Possible hypotheses to explain the 1979 results include the <br />possibility that incoming radiation may be dissipated more slowly under <br />.excelsior, especially when extensive vegetation cover is present. The <br />4BEXN plot contributed the greatest production of any plot sampled. T'ae <br />greater cooling effect by excelsior oa the 4:1 south plot is attributed <br />to the very poor vegetative cover of both the control and straw treat- <br />ments on this aspect. Since most of the stray blew away, the straw <br />treatment behaved more like the control. The behavior of the excelsior <br />mulch on the 2:1 south plots was similar to that in 1978; the results on <br />~ the north aspect suggest that eacelsior may be losing its greater <br />insulating capabilities. <br />The west-facing plot temperature pattern is similar to that re- <br />corded for 1978. Excelsior mulch provided cooler near-surface tempera- <br />.rures than hydromulch and fewer fluctuations in response to changes in <br />ambient condition. <br />The topsoiled level plot vas consistently cooler at near-surface <br />depths than the refuse level plot. It would be expected that the black <br />refuse material would absorb greater amounts of radiation than the brown <br />topsoil. The refuse material was not noticeably warmer at depth than <br />the topsoiled treatment. <br />The 1979 data show that 4:1 slopes were slightly warmer than 2:1 <br />slopes, but differences are not great oa either north or south aspect. <br />Larger differences were noted between aspects. South aspects on both <br />slopes were 5-lOF warmer than counterparts on the north. This tempera- <br />ture difference in response to aspect is mirrored by the response of <br />vegetation to aspect. !Such greater production and density were recorded <br />22 <br />