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• Species Diversity and Composition <br />Species density reflects the total number of species present (richness) in 100 square meters <br />one meter to either side of the 50m cover sample transects. Species density data are <br />summarized in Table 5. Mean species density of 33.5 species/ 100 m2 was up slightly from <br />1996 levels (32.5 species/ 100 mz) and approached the values of 36.0 and 38.2 species/ 100 <br />m2 observed in the Seneca II reference areas. Mean native species density slightly exceeded <br />that of the Seneca II 1990 reclaimed area. <br />Sample Adequacy <br />A summary of sample adequacy calculations for the parameters of cover and woody plant stem <br />density is presented in Table 7 (Appendix 1). Although there was no attempt to achieve <br />sample adequacy during this monitoring study, minimum sample size was calculated for <br />genera! information. As can be seen in Table 6, sample adequacy was achieved for cover but <br />not for herbaceous production or shrub density sampling. <br />Noxious Weeds <br />• Of plant species observed during 1997 sampling, Canada thistle (Cirsium arvense, aka Breea <br />arvensis) is listed state-wide among the top ten noxious weeds (C.R.S. 1996). Downy brome <br />(aka cheatgrass, Bromus tectorum or Anisantha tectorum), houndstongue (Cvnoolossum <br />officinale), and bullthistle (Cirsium vulaare) are also listed as noxious in Colorado. <br />Houndstongue is regretfully widespread in the native vegetation, mainly in heavily grazed areas. <br />Canada thistle has been observed previously in the 1991/1993 Seneca II-W reclaimed areas. <br />Climatic Conditions <br />Precipitation data by month from the Seneca II-W Mine for 1993, 1994, 1995, 1996, and 1997 <br />as well as the 10-year average for the mine are shown in Figures 1 a and 1 b. As can be seen in <br />those graphs, 1993 had been a relatively favorable precipitation year, but beginning in <br />November 1993 and continuing through 1994, only two months (April and November) even <br />reached average precipitation. In 1995, however, January, February, and March were close to <br />average, and April and May were far above normal (with a total of over eight inches in those two <br />months). For 1996, precipitation returned closer to normal with below average amounts in <br />March and August of 1996, and in 1997, spring (and the preceeding fall) moisture was above <br />• average. <br />8 <br />