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• of sample size was determined with the minimum sample size equation and <br />the total vegetation cover from each of 20 transects. The minimum sample <br />size was calculated as 5.26 or 6. Thus, the 20 transects represent an <br />adequate sample with respect to cover. The old field community consists <br />of 45 percent vegetation, 28 percent bare soil, 25 percent litter, and 2 <br />percent rock. The community species composition for all species com- <br />prising 3 percent or more of the vegetation cover are shown in Table 34. <br />Woody plant density determinations for fifty lm x 50 m transects <br />in the old field community were made and are summarized in Table 35. <br />The woody plant density for each transect was entered in the minimum <br />sample size equation which indicated 154 transects would be required as <br />a minimum sample size. The density of 13 woody plant species is 2,680 <br />individuals per acre. The prevalent species include rabbitbrush (50 <br />percent), broom snakeweed (18 percent(, big sagebrush 112 percent!, and <br />mountain mahogany 111 percent) which account for 91 percent of the woody <br />plant density in the old field community. <br />Herbaceous production was determined in the old field community <br />by clipping 1 m plots at the origin of each transect by species for a <br />total of 50 plots. Oven dried weights of each species for each clip <br />plot were determined to the nearest 0.1 gram. Data is summarized in <br />Table 36. The minimum sample size was calculated as 77. Production for <br />1982 in the old field is estimated at 951 kg/ha or 844.5 pounds per acre. <br />• This old field exhibits good vegetative cover at 45 percent <br />and fair herbaceous production. The dominant species is cheatgrass which <br />has a low density. The slope, aspect, and elevation do not appear to be <br />controlling production. Soils are deep and do not appear limiting except <br />for high clay content and only poor-fair texture. The area's past manage- <br />ment included brush and tree chaining and burning and some contour <br />furrowing. The area was reseeded with introduced grass species and was <br />grazed until 1979 when the field was abandoned. The area still shows <br />evidence of overgrazing by the existing dominant species composition. <br />This grassland is apparently in a stage of succession. The area, if left <br />alone, would probably eventually evolve into a mountain shrub community <br />and finally to a climax pinyon-juniper community. Inspection of SCS <br />aerial photographs indicate undisturbed, older terraces in the area <br />exhibiting similar slope, aspect, elevation, soils, etc. are predominantly <br />vegetated by the pinyon-juniper community. <br />No suitable old field reference area is available within <br />the lease area, and the current species composition is undesirable from <br />a wildlife habitat post-mining land use standpoint. <br />6.3.2 Cultivated Field <br />The cultivated field vegetation community consisted of dryland <br />wheat. The farmer reported that production ranges from 18 to 21 bushels <br />per acre (letter follows(. At 60 pounds per bushel, this amounts to an <br />• annual production of 1,080 to 1,260 pounds per acre. <br />-24- <br />