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• <br />ERO Resources <br />The nature of the vegetation mosaic that predominates the Poserado Mine <br />permit area has created special problems in evaluating the influences that <br />are responsible for the character and distribution of the vegetation <br />types. In any semi -arid ecosystem a predominant patchiness occurs in the <br />vegetation. This internal variability is controlled by environmental <br />factors or complexes of factors. The cause -and -effect relationships <br />resulting can usually be ellucidated and described within degrees of <br />confidence. Once these features are examined and understood, their <br />effects are relatively constant and are locally reproduced within a range <br />of influence. In the case of the mosaic occurring on the mine permit <br />area, with its history of abuse from sheep grazing, the controls on the <br />patchiness of the vegetation are complicated by random events that have <br />little or no predictable pattern. The use of the area by sheep and the <br />effects of this use on any given area or vegetation type are not constant <br />in terms of degree or intensity. The only reliable patterns that can be <br />found are the heavy use of south- and southwest -facing slopes near roads <br />• by sheep (cf. McDaniel and Tiedeman 1981). However, this use is <br />apparently not equal among years for any given site having these <br />characteristics. Moreover, the understanding of this random use by sheep <br />does not provide sufficient information to relate vegetation damage and <br />predict species responses. The net result of this situation is that sheep <br />introduce a degree of randomness that creates a potential unnatural <br />variation within any vegetation type on the permit area. Since this <br />random variation is not part of the vegetation dynamics it can only be <br />accounted for in sampling adequacy attempts by fortuitous chance. <br />• <br />Methodologies used to accomplish sample adequacy calculations and the <br />various analyses to which data were subjected have been discussed in the <br />methods section. The types of calculations and tests performed included: <br />o Sample Adequacy (Snedecor and Cochran 1967) <br />o Student t -testing (for paired affected and reference areas) <br />II.F-81 <br />