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sampling was done. It does not tell what was produced and consumed by wildlife <br />• or livestock or what has already died and fallen to the ground as litter. <br />Moreover, grazing may stimulate vegetative growth, thereby increasing the total <br />production potential over a growing season (Smith et al, 1962; National Academy <br />of Sciences, 1962). It is extremely difficult, if not physically impossible, to <br />accurately quantify such biomass potential. <br />Production has historically been measured to indicate the amount of useful <br />production available to grazing animals as opposed. to total production. The <br />amount of useful production depends on many variables such as: the species of <br />herbivore; the plant species; the physical availability of the forage; and the <br />proximity of other essential habitat such as water, cover, etc. (Lucas, 1962). <br />Sheep, for example, will select and use plant species that cattle may not <br />(Heady 1975). Deer will commonly use forage up to four and a half feet off <br />the ground, while sheep generally don't graze above three and a half feet. <br />(Bureau of Land Management, 1963). As shrubs become too dense, they begin selec- <br />tively precluding animal access and even forage close to the ground becomes <br />i� unavailable to some ungulates (Kufeld, 1977). Usable forage must, therefore, be <br />defined for each area before a method of evaluating successful reestablishment of <br />productivity can be finalized. Without the concept of usefulness incorporated, <br />production data have little meaning for evaluating pre and post -mining utility, <br />or value, of vegetation. <br />Measuring usable biomass from shrubs is a tedious chore that requires a sub- <br />jective judgement of what is current annual growth as well as an assumption of <br />the maximum grazing height of herbivous using the area. Further, though it is <br />documented that shrub density affects animal use, the effects have not been <br />quantified. Boyd (1970) for example, found that oak brush densities (cover) in <br />excess of 51% precluded elk use while densities as low as 352 inhibited use by <br />elk. Unpublished research at Utah International, Inc's Trapper Mine near Craig, <br />Colorado, shows that sheep use in oakbrush is inversely related to stem density <br />-5- <br />r n ? eIM9? <br />