Vegetation response to elk population and habitat management in Rocky Mountain National Park: Analysis of elk and vegetation management plan monitoring data, 2008-2023

Fifteen years ago, Rocky Mountain National Park (RMNP) implemented an Elk and Vegetation Management Plan (EVMP) in response to increasing negative impacts of winter elk herbivory on key plant communities. The EVMP is intended to guide the management of elk and vegetation over a 20-year period, reduce the impacts of elk on vegetation, and bring target ecosystems into the natural range of variability for elk and vegetation in aspen, montane riparian willow, and upland herbaceous habitats. Monitoring plots were established at the outset and vegetation data is collected, analyzed, and results are reported every 5 years. These results are used by managers to modify management actions as needed to improve the condition of key habitats on the elk winter range. A small number of aspen and willow sites are also monitored in the Kawuneeche Valley, an elk summer range area that has experienced willow and aspen decline from summer elk herbivory as well as several decades of moose herbivory. After 15 years of EVMP management, results are mixed. Progress toward improved habitat that was observed through the first 10 years appears to have plateaued in the last 5 years, likely due to several additional factors, namely an increasing moose population and large wildfires which affected EVMP aspen and willow sites. Aspen regeneration and recruitment has steadily increased since baseline and, by 2023, was just short of reaching the 20-year EVMP objective, but most progress has been inside protective fences. Aspen stand structure has improved, but only inside fences and in unfenced, noncore winter range. Willow height increased by 43% relative to baseline conditions and willow cover nearly doubled over the entire winter range, however these increases were mostly limited to fenced areas. Noncore winter range showed only modest willow height and cover gains, while no significant change was observed on unfenced core winter range despite a ~50% reduction in browse intensity. In the Kawuneeche Valley, unfenced willow and aspen have continued to decline. The level of elk grazing on winter range upland herbaceous vegetation has been successfully reduced and no additional grazing-related changes appear to be taking place. Although many EVMP objectives have been met after 15 years, the habitat fences are key to maintaining patches of high-quality habitat and we advise against removing them until other components of the system (beaver communities, restoration of hydrologic regimes, willow recruitment, stable elk and moose populations) are functioning.