2011-03-30_REPORT - C1980005 (2)

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