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o.o. <br />• <br />2.6 TREE DENSITY SAMPLING <br />The density of trees in forested vegetation types was measured by counting tree stems (greater <br />then 1 inch diameter ei breast height) rooted within e 5 m x 50 m belt transact, ezniered along <br />the shrub density transact. Typical maximum tree heights were noted in each sample stand. <br />Also the B9e of trees in the dominant tree diameter classes was determined using an increment <br />borer. <br />2.7 REFERENCE AREASAMPLINO <br />The reference areas sampled es pert of this study were those already delineated for the Seneca I I <br />Mine for the Mountain Brush end Sagebrush vegetation types. Cover, herbaceous production, end <br />shrub density date were gathered using the same methods es were used in the Cypress affected <br />area. <br />2.8 DETERMINATION OF SAMPLE ADEQUACY <br />The adequacy of quantitative sampling in the Cypress Area studieswes examined using the <br />following formula: <br />nmin = (s~t~) / (d2xz) <br />where nmin minimum sample size <br />s = standard deviation (n-1) <br />t = two tailed t-value at 90 ~ level of confidence (alpha = 0.1; t =1.645) <br />d = desired level of detectable reduction in the mean (10 ~ or0.1) <br />x = arithmetic mean <br />Except far production, sampling was continued in the field until either sempte adequacy was <br />achieved for a particular parameter or the prescribed maximum number of samples was leken. <br />Experience had shown that the difficulty of following statl5ticel progress during collection of <br />production samples was greaser than that of collecting the maximum number of samples. These <br />• maxima were developed during Peabody consultation with CMLRD staff prior to the beginning of <br />-4- <br />