摘要：Ungulate impacts on woody vegetation have been a concern on Montana wildlife habitats for more than a half-century. Fenced areas restricting access of all ungulates (exclosures) were established between 1944 and 1988 on many habitats to evaluate ungulate impacts on shrubs. Our objective was to determine the effect of long-term browsing on big sagebrush (Artemisia tridentata), bitterbrush (Purshia tridentata), curlleaf mountain mahogany (Cercocarpus ledifolius) and horizontal juniper (Juniperus horizontalis). We hypothesized that the long-term effect of ungulate browsing would not impact these common shrubs. Canopy cover and density of shrubs were measured in and out of exclosures (n =14) on environmentally paired sites. Big sagebrush canopy cover, density of mature big sagebrush, and production of winter forage (n =7) were greater with protection on four sites (P ≤ 0.05). Differences were not restricted to one subspecies of big sagebrush. Bitterbrush canopy cover and density of mature shrubs (n =3) were greater with protection on two sites (P ≤ 0.05). Curlleaf mountain mahogany canopy cover (n =2) was greater with protection on both sites (P ≤ 0.05), while density of mature mahogany was greater at one site (P ≤ 0.05). Horizontal juniper cover (n =2) was greater with protection at both sites (P ≤ 0.01). We rejected our hypothesis at ten of the 14 sites evaluated. Long-term ungulate browsing has impacted shrubs at ten sites that are not geographically related. This has implications to plant communities and value of shrub habitats to wildlife.
