Laserfiche WebLink
n <br />U <br />Vegetation Measurements for Bond Release: New Homm~ Mine NH1 f0 Aae Site and Reverence Area <br />points (spaced at 10 an) at each 10-foot interval, providing 100 cover measurements per <br />transed. Intercept was recorded as bare ground, litter, rods, or plant species. The total number <br />oT °hits" for each plant species or substrate type was summed for each transeG to determine <br />percent cover. <br />Cover samples were taken at the random sample points in order; until sample adequacy was <br />reached according to the following formula: <br />Nmin = (st)Z / (dX)2 <br />where <br />N,,,;° =minimum sample size <br />s =sample standard deviation <br />t =single tailed t-value at the 90% confidence interval (alpha = 0.10), with infinite <br />degrees of freedom (t = 1.645) <br />d =desired level of reduction about the sample mean (0.10) <br />x =sample mean <br />Sample adequacy was determined in the field by summing measurements of total live perennial <br />vegetation (excluding state-listed noxious weeds) for each transed, and using a Microsok Excel <br />spreadsheet on a laptop computer to periodically calculate Nmh. <br />For each transed, percent cover for each plant species and substrate type was summed from <br />field data sheets, and sums calculated for unvegetated, noxious weeds, annual grasses, annual <br />forts, shrubs, perennial grasses, and perennial forts. Sums Tor plant species groups excluded <br />noxious weed spedes. <br />Production Measurement <br />To measure herbaceous production, random sample points were located in the field, using the <br />randomly selected points described above for cover transeds. At each sample point, a 3 x 3 <br />foot (9.0 ft~) square sampling frame was thrown over the shoulder. All above-ground <br />herbaceous vegetation (current year growth) in the sampling frame was Gipped. At the <br />reference area the frame was Gipped, then flipped once in a random direction and clipped again <br />to increase the size of the Gipped area to 18.0 ftz, because of the patchy distribution of <br />herbaceous vegetation. <br />Clipped vegetation was placed in paper bags, sorted by perennial grass, annual grass, <br />perennial fort, annual fort, and sutrshrub. State-listed noxious weeds were excluded from <br />Gipped material. Clipped vegetation was air-dried during wane sunny weather for at least 72 <br />hours, and weighed. Weights were converted to pounds per acre, and mean and standard <br />deviation or total live vegetation calculated. <br />Sample adequacy was calculated after weights ware determined, according to the formula <br />described above for cover. Fifteen sample plots were initially clipped at each site. After <br />calculating sample adequacy, we returned to the field and clipped additional plots at the <br />reference area to reach sample adequacy. At the NHt 10.acre site, Nmo was calculated to <br />BIO-Log/c Environmental <br />September 2005 <br />• <br />12 <br />