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The trends in herbaceous cover over the years on the depth-of-sand <br />plots help explain the seriousness of sand compaction as well as relative <br />year quality, because clay shale under just one foot of sand tended to <br />compensate for compaction. The trends on one foot of sand show that plant <br />growth in 1979 ti+as indeed very near that attained in 1978, as one would <br />judge by total amounts of water received. FLrthermore, growing-season <br />precipitation in 1980 was a little less than half as much as in 1979, <br />which corresponds with the decrease in herbaceous cover from 42 to 19%. <br />By contrast, herbaceous cover attained by plants on 2 and 3 feet of sand <br />decreased to about half as much in 1979 as in 1978, and decreased again <br />to about half as much in 1980 as in 1979--statistically equal to values and <br />trends on the mulch-comparison plots. <br />There was one other serious effect of sand compaction. Botanical <br />composition has changed to greater dominance by sand dropseed rather than <br />to the tall grasses prairie sandreed and sand blues tem. <br />Thus, in the reclamation of mined areas, sand should be placed over <br />the shale in layers as thick as possible with a minimum amount of traffic, <br />and preferably when the sand is dry to prevent compaction. Even then, <br />ripping may be needed before seeding. <br />INDIVIDUAL SPECIES PL015 <br />Herbaceous cover. of individual species was sampled six times in the <br />three years to obtain neaz maximum cover for each species (Table 1). <br />'darvi-season grasses generally attained greatest cover in 1978, then <br />decreased a little in 1979 and decreased further in 1980; whereas, the cool- <br />season species generally attained greatest cover in the second year, and <br />decreased in 1980 to a lesser extent than warm-season grasses. Winter <br />and spring precipitation aze most important to cool-season plants, but <br />growing-season precipitation is most important to warm-season plants. <br />Among the species included in our seed mixture for all other plots <br />in this study, all except Indian ricegrass have performed adequately. It <br />is especially encouraging to find that prairie sandreed, which started with <br />thin stands, has increased. <br />Among the species not included in the seed mixture, those most worthy <br />of consideration for inclusion at a lox rate (for increasing species <br />diversity) in the reclamation seed mixture aze as follows: <br />Sxitchgrass <br />Giant dropseed <br />Alfalfa <br />Smooth brome <br />Pubescent xheatgrass <br />Crested xheatgrass <br />Thickspike xheatgrass <br />Russian wildrye <br />• <br />7 <br />