Through the study of historical records, photographs, and current vegetation measurements inside and outside of grazing exclosures, the authors determined that high elk (Cervus elaphus) populations were the major cause of aspen (Populus tremuloides) declines in Rocky Mountain National Park. Historical records and tree ring data indicate that aspen regeneration was not affected by climactic events, beaver populations, fire suppression and conifer encroachment, but rather, was almost directly related to elk population size. In periods with low elk populations, aspen regeneration was successful, while high elk populations limited regeneration. Grazing exclosures provide further evidence to support the negative effects of elk browsing, as aspen cohorts inside exclosures had a greater number of live trees, with more live branches and less bark stripping, than cohorts outside of the exclosure. Also, cohorts inside exclosures were continuing to regenerate and reach above elk browsing height, while this was not true outside of exclosures. The data from this study suggest that elk are the major factor impacting aspen regeneration on the winter range in Rocky Mountain National Park. The park's natural regulation policy has not maintained the elk population at a level that is sustainable for vegetation on the current winter range.
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.