Mule deer-induced mortality of mountain big sagebrush

Abstract

A fence line contrast was provided by a deer fence that bisected a mountain big sagebrush (Artemisia tridentata ssp. vaseyana) community. The sagebrush community was located on an exposed, west-facing slope that was generally swept free of snow during the severe winters of 1982-83 and 1983-84. On the freeway side of the fence, the site was essentially free of browsing animals, while above the fence, the shrubs were exposed to concentrations of mule deer (Odocoileus hemionus). Considerable big sagebrush mortality was evident after the 2 successive winters of heavy snowfall. Big sagebrush mortality and partial dieback of portions of the canopy were significantly (P<0.05) higher in the portion of the community exposed to browsing. Herbaceous species composition also differed between the protected and browsed areas with a higher portion of annual species found in the browsed community. A large number of big sagebrush seedlings germinated in 1984, but failed to establish by 1986. Excessive use of native plants by native large herbivores can have lasting effects on plant communities.