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• d = Precision (0.10 for cover and production; 0.15 for <br />woody plant density) <br />x = Sample arithmetic mean <br />t = The (a=.10) t-table value for a 1 tail West, n-1 degrees of <br />freedom (infinite degrees of freedom may be used if <br />n>30) see Rohlf and Sokal 1969 <br />n =Sample size <br />All such calculations were based on data from a minimum of fifteen samples. <br />The achievement of sample adequacy for herbaceous cover based on first-hit data is especially <br />difficult in mountain brush vegetation. This is the case because the abundant though variable <br />woody cover "shields" ground level herbaceous cover, absorbing first-hits (always projected from <br />above) before they reach the herbaceous ground layer. Thus first-hits on herbaceous cover are <br />generally few, though in some locations, sparse tall woody cover will allow many; the result is a <br />highly variable dataset and hence difficulty in achieving sample adequacy. Use of all-hit data <br />however allows the full extent of herbaceous cover to be "seen." With this in mind, an approach <br />to calculating sample adequacy in the Mountain Brush Reference Area using all-hit herbaceous <br />. cover was proposed to DRMS (see Appendix 7). Once sample adequacy was achieved based on <br />all-hit herbaceous cover, the ratio of first-hit to all-hit herbaceous cover would be assessed for <br />sample adequacy. Then the all-hit mean herbaceous cover would be converted to a first-hit basis <br />using this ratio and that converted value would be used in the calculation of the performance <br />standard along with the first-hit cover value from the Sagebrush Reference Area. First-hit sample <br />adequacy in the latter area has historically proven to be more easily achieved. <br />NOTES ON THE COMPARISON OF DATA TO APPLICABLE REFERENCE AREA STANDARDS <br />Upon the formal comparison of cover data from reclaimed areas to applicable performance <br />standards, observed total first-hit herbaceous cover percentage must be adjusted for excessive <br />contribution by annual / biennial species (CDMG 1995, Guidelines Regarding Selected Coal Mine <br />Bond Release Issues, 1 (IV)A(4)). Herbaceous cover values used in such comparisons also must <br />exclude values for species present on the Routt County Prohibited or Restricted Noxious list or <br />that are listed as noxious by the State of Colorado (Colorado Dept. of Agriculture, Division of <br />Plant Industry, Title 35, Article 5.5, 101-119, Lists A and B of Rules as replaced 2003). <br />For purposes of assessment of reclamation adequacy, first-hit herbaceous cover data from <br />reference area sampling are used. <br />0 5