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o.o. <br />• <br />2.6 TREE DEN5ITY SAMPLING <br />The density of trees in forested vegetation types was measured by counting tree stems (greater <br />then 1 inch diameter et breast height) rooted within o 5 m x 50 m bell transact, centered along <br />the shrub density transact. Typical maximum tree heights were noted in each sample stand. <br />Also the age of trees in the dominant tree diameter classes was determined using en increment <br />borer. <br />2.7 REfERENCEAREASAMPLINO <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, and <br />shrub density data were gathered using the same methods es were used in the Cypress effected <br />arse. <br />2.8 DETERMINATION Of SAMPLE ADEQUACY <br />The adequauy of quantitative sampling in the Cypress Aree studieswes examined using the <br />Following formula: <br />nmin = (sZiz) / (d2xZ) <br />where nmin = minimum sample size <br />s = standard deviation (n-1) <br />i = 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 for production, sampling was continued in the field until either sample adequacy was <br />achieved for a particular parameter or the prescribed maximum number of samples was taken. <br />Experience had shown that the dffflculty of following stetlsticel progress during collection of <br />production samples was greater 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 />