Sagebrush response to ungulate browsing in Yellowstone.

Abstract

Big sagebrush (Artemisia tridentata Nutt.) declined from ungulate browsing during the first half of the twentieth century on the Northern Yellowstone Winter Range. It was our objective to compare shrub parameters of Northern Yellowstone Winter Range sagebrush habitat types continually browsed or protected for 32 to 37 years. Measurements were taken in and out of exclosures for 19 environmentally paired, protected, and browsed sites. We found significant differences in development between protected and browsed shrubs. Big sagebrush canopy cover at the 19 sites averaged 19.7% with protection and 6.5% where browsed (P less than or equal to 0.0027), and plants were twice as numerous (P less than or equal to 0.0027) under protection. Winter forage production of individual big sagebrush plants was also greater under protection at 16 of the 19 paired sites (P less than or equal to 0.0027). Subdominant sprouting shrubs generally responded the same as big sagebrush. This ungulate induced decline of shrubs has implications for many Northern Yellowstone Winter Range values. Ultimately many organisms are sacrificed with the loss of quality big sagebrush habitat.