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U <br />ERO Resources <br />Sagebrush-Wheatgrass/Sagebrush Complex <br />This complex is dominated by the Big Sagebrush-Wheatgrass vegetation <br />type. Big sagebrush areas that exhibit high cover values are inclusions <br />in the type resulting from surface disturbance. The dense sagebrush <br />stands are postclimaxes formed as the end result of overgrazing and <br />maintained by the erosional cycles established by overgrazing (0aubenmire <br />1942, Costello 1944). Soils underlying the dense sagebrush inclusions <br />tend to be somewhat deeper than those characterizing the sagebrush- <br />wheatgrass type. The deeper soils tend to favor not only the persistence <br />of sagebrush, but also the post -climax increases in this species due to <br />sheep grazing and traffic. The deeper soils are favorable to the <br />sagebrush because of higher available soil moisture conditions. In <br />addition, the sagebrush inclusions sometimes demonstrate more coarse soils <br />than the adjacent sagebrush-Wheatgrass sites. The sandy soils have lower <br />available soil moisture characteristics at the surface. Subsequently, the <br />• sites do not favor herbaceous growth initially. The increased <br />environmental adversities created by grazing and animal traffic, and <br />perpetuated as cycling erosional events are additional deterrents to any <br />development in the herb layer. Rabbitbrush is common in the sandy soil <br />areas and is a reliable indicator of the presence of the dense sagebrush <br />inclusions. <br />• <br />Sagebrush-Wheatgrass/Western Wheatgrass Complex <br />This lateral gradient interrupts the overall gradient on sideslopes Map <br />128, Pocket). The Big Sagebrush-Wheatgrass vegetation type is the major <br />component of this complex. The western Wheatgrass inclusions are patchy <br />and apparently somewhat restricted by soil characteristics. Western <br />wheatgrass has been reduced or eliminated from many sites on which it was <br />formerly common. The small sites this species now occupies act like <br />refuges for the remainder of much of the population. Soil depth and <br />texture are important determining factors in the complex. The grass <br />II.F-22 <br />