03005naa a2200421 a 450000100080000000500110000800800410001910000170006024500890007726000090016652019490017565000140212465000210213865000110215965000110217065000110218165000120219265000150220465000130221965000100223265000190224265000150226165000110227665000120228765000110229965000200231065000200233065300130235065300150236365300140237865300190239265300230241165300240243465300150245865300210247365300230249477300660251715204852023-12-11       1965    bl uuuu     u00u1 u    #d1 aSMITH, A. D.  aDetermining common use grazing capacities by application of the key species concept.  c1965  aCorrect substitution rates of one grazing animal for another under common use are uniform, being governed at any point by the utilization standard of some single species. This key species may vary at different levels of animal combinations, thus changing the rate of substitution to another but still constant rate. Under certain conditions, common use can add capacity in one direction only, e.g. when the animal to which the range is less suited is substituted for the other. In this case the best suited animal alone provides maximum grazing capacity. The capacity under common use may be greater than that realized with the less suited animal alone, or greater than either animal alone, depending upon the particular combination of animal numbers that are present and the particular range. No blanket statement may be made that common use increases grazing capacity. Each situation must be determined independently upon the basis of animal preferences and the forage present. Administrative problems and social objectives, which were not considered here, may justify allocations of range resources on other bases than grazing capacity. Table 1. Forage factors reported by Cook (1954) reanalyzed to illustrate indicator species concept; Table 2. Utilization and percent of diets of major forage species for deer (D) and sheep (S) on study area in Logan Canyon, Utah; Table 3. Calculated grazing capacities of a range for selected combinations of deer and sheep with two key species; Table 4. Utilization by deer and cattle on a deer winter range near Fillmore, Utah, used by cattle spring and fall and calculated forage factors under common use; Figure 1. Theoretical cumulative utilization of three plant species during the grazing season; Figure 2. Substitution curves between mule deer an(l cattle near Fillmiore, Utah, and mule deer and sheep near Logan, tUtah; FIigure 3. Theoretical substitution curves under five different situations.  aAgropyron  aAnimal nutrition  aBromus  aCattle  aElymus  aGrazing  aHarvesting  aLathyrus  aSheep  aSymphoricarpos  aThalictrum  aBovino  aCaprino  aManejo  aNutricao animal  aPastagem Nativa  aBig game  aCommon Use  aGrassland  aGrazing animal  aGrazing Capacities  aKey Species Concept  aManagement  aRange Production  aSubstitution Rates  tJournal Range Managementgv. 18, n. 4, p. 196-201, Jul. 1965.