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• production estimated for 1990 was found to be 3652.6 Ib/acre (Table A12). Shrubs do not occur <br />in this type, though the areas involved were probably originally Mesic Drainage. <br />In the Supplemental Area (Table B6), total top-layer cover in the Improved Pasture -Subirrigated <br />type was 80.0 percent, bare soil was 0.9 percent, and litter was 19.1 percent. This type in the <br />supplemental area was not as intensively used for agricultural production as the area of this type in <br />the baseline area. Its plant cover was greater and bare soil less than the baseline area, where the <br />values were 68.9 and 5.7 percent, respectively. Species density was 20.5 species per 100 sq. m. <br />Production was 2632 Ib per acre in 1992. <br />The following discussion describes species dominance in the Improved Pasture -Subirrigated <br />vegetation type based on the all-laver relative cover values. All percentages given in the following <br />three paragraphs refer to this cover statistic. <br />The Improved Pasture -Subirrigated vegetation type was dominated by grasses and (orbs. Eight <br />native perennial grass species were encountered with a total of 42.3 percent cover and 100 percent <br />• frequency, and six introduced perennial grasses contributed 30.9 percent cover and 100 percent <br />frequency. Native perennial (orbs had 27 species for a total of 8.9 percent cover and 100 percent <br />frequency, while the introduced perennial (orbs were much less diverse with only 7 species, but <br />with a greater cover of 10.3 percent and 100 percent frequency. The combined (introduced plus <br />native) annual and biennial forts were significant contributors to cover with 6.8 percent cover and <br />86.7 percent frequency. Shrubs were never well developed and did not contribute to cover but <br />could be found mixed with the grasses and (orbs. Quaking aspen suckers or seedlings were also <br />encountered but were not a significant component of this community. <br />Cover dominance was shared by the native and introduced perennial grasses, accounting for 42.3 <br />and 30.9 percent, respectively. The dominant native perennial grass was Agassiz bluegrass with <br />34.7 percent cover and 100 percent frequency. Mountain brome contributed 4.2 percent cover and <br />smallwing sedge had 2.5 percent cover. The dominant introduced perennial grass was smooth brome <br />with 10.6 percent cover and 93.3 percent frequency. The other introduced grasses that contributed <br />between 1 and 6.6 percent cover were intermediate wheatgrass (Thinopyrum intermediuml, <br />redtop, tall fescue fFestuca arundinaceal, timothy, and orchard grass (Dac lis glomeratal. The <br />dominant native perennial fort was western yarrow with 3.7 percent cover and 100.0 percent <br />• frequency. Showy fleabane, with 1.5 percent cover, was the only other species among the 27 in <br />this growth form that had a cover value above 1 percent. The codominant introduced perennial <br />15 <br />