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I • 2.2 Species Composition <br />Quantitative vegetation cover information by species has been collected at the reference <br />azea and the reclaimed areas since 1994. This data has been refined to show relative cover <br />of plant species in each of the areas sampled over that period of record. Based on the <br />eight years of data from the Osgood Sand Reference Area, a picture of the species <br />composition of the reference area was developed. Initially, a record of all vegetation <br />species was made and plotted to identify the species that contributed significantly to the <br />cover of the community. From this record, the species that contributed three (3) percent <br />relative vegetation cover for more than half the period of record were identified, and their <br />contributions plotted. The three percent relative percentage cutoff is that used by the <br />Colorado Division of Minerals and Geology as the selection criterion for major species in <br />determining species composition requirements for the species composition revegetation <br />success criterion. <br />3.0 RESULTS <br />3.1 Comparisons of Precipitation Regimes <br />January-July <br />Initial evaluations of the relationship between vegetation pazameters and precipitation at <br />• the Keenesburg Mine indicated that the accumulated precipitation value from January <br />through July would serve as a suitable predictor of total vegetation cover and total <br />herbaceous production (Savage, 2000). This time period was selected as the segment of <br />the year during which the majority of precipitation occurred at the Keenesburg Mine. <br />Figures 1 through 4 illustrate the relationship of the cumulative January-July precipitation <br />amount and total vegetation cover and total herbaceous production at the Osgood sand <br />reference area and the reclamation areas. <br />The best-fit derived equation and plot reveal excellent correlation between January-July <br />precipitation and total vegetation cover at the Osgood sand reference area (Figure 1). The <br />form of the equation is a thud order polynomial generally indicating an increase in total <br />vegetation cover over increasing precipitation with a corresponding decrease in the rate of <br />increase in cover with increasing precipitation over the range of sample values. This is an <br />expected form of a relationship between cover and precipitation and is reasonable in terms <br />of observations at the reference area over the past eight seasons. <br />The relationship between January-July precipitation and total vegetation cover at all <br />reclamation areas {Figure 2) was less definitive. The best-fit equation yielded a correlation <br />coefficient (RZ) of 0.6877. The relationship between January-July precipitation and total <br />vegetation cover for all the reclamation areas explained only 68.77 percent of the variation <br />in the data (compared with 91.32% at the reference area). Further, the form of the best-fit <br />• equation was that of an exponential, not the polynomial as in the reference area, and not <br />_~ <br />