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FRO Resources <br />noteworthy that although cheatgrass occurs in the western wheatgraca type, <br />• its importance is low. The major factor attributed to this relationship <br />is the loss of competitive advantage to the cheatgrass in heavy clay soils <br />on which the western wheatgrass refugia stands occur. <br />Scattered shrubs occur in the cheatgrass-annual forb type, but no true <br />shrub layer exists. Large numbers of certain shrub species do occur, <br />however. Total mean shrub cover in this type is 21.8X. Of this value big <br />sagebrush accounts for 93X of the total or a mean cover value of 20.2X. <br />Other shrubs 'that occur but are of less importarae are little rabbitbrush <br />- 0.6X, spiny hopsage - 0.4X, greasewood 0.3X, fourwing saltbush - O.IX <br />and Gordon saltbush - O.1X (Figure 4, Table 61. Shrub dens itiee are big <br />sagebrush - 14,137/Ha, little rabbitbrush - 875/Ha, fourwirg caltbush - <br />512/Ha, greasewood - 362/Ha, spiry hopaage - 325/Ha and Gordon caltbush - <br />175/Ha (Table 71. <br />Primary productivity for the oheatgrass-annual forb type is highly <br />variable. @iomase production apparently is reliant upon the amount of <br />• cheatgrass and western wheatgrass versus the importance of annual fortis. <br />Annual fortis do not produce a significant amount of biomass, so that a <br />large amount of these species in a site reflect low primary productivity. <br />Productivity in the sites sampled averaged 3.9 g/m2. The former value <br />ie the lowest obtained for the permit area (Figure 5, Table 91. Important <br />grass producers in this type with mean production values are western <br />wheatgrass - 2.3 g/m2 and cheatgrass - 0.6 g/m2. The above grasses <br />produce 74X of the total biomass. Fortis that contribute to production are <br />baby blue eyes - 0.2 g/m2, actor - 0.1 g/m2, peppergrass - 0.1 g/m2, <br />stickseed - O.1 g/m2 and fleabane daisy - <0.1 g/m2 (Table 91. <br />f3) A!ccession and Land Use: <br />The cheatgrass-annual forb vegetation type is a highly successional <br />vegetation type. Thic type has replaced mixed grasslands dominated by <br />western wheatgrass and other perennial grasses. It is apparent that <br />overgrazing in the pretence of annual irrvaders was the principal factor <br />r 1 <br />U <br />II.F-47 <br />