Appropriate use levels have not been established for wildlife browsing of true mountain mahogany (Cercocarpus montanus) and this study used exclosures at 5 sites to determine how natural levels of ungulate herbivory affected the plant cover, diversity and species composition of true mountain mahogany plant communities in Utah. Utilization varied by year, site and herbivore species. Unbrowsed plants were generally wider, taller and had greater percent cover than browsed shrubs. Plant community structure and species richness and diversity were similar inside and outside of the exclosure, however, species composition of forbs, shrubs, and graminoids varied slightly between the grazed and ungrazed areas. True mountain mahogany is highly tolerant of winter browsing, and can compensate for >100% utilization of annual growth by increased growth during wet years. However, continued use of 100% of annual growth could reduce cover, shrub size, and forage production during years of lower resource availability. The authors suggest a management approach is to monitor cover and size of shrubs inside and outside well-placed exclosures across the winter range over time, and reduce herd numbers as appropriate to allow browsed shrubs to maintain or reach the size of unbrowsed shrubs when their growth has leveled off after a few years of exclusion.
Citations and enhanced abstracts for journals articles and documents focused on rangeland ecology and management. RSIS is a collaboration between Montana State University, University of Idaho, and University of Wyoming.