Vegetation Responses to Natural Regulation of Elk in Rocky Mountain National Park
NATIONAL BIOLOGICAL SERVICE FORT COLLINS CO MIDCONTINENT ECOLOGICAL SCIENCE CENTER
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Little experimental information is available on the relationships between herbivory by native ungulates and vegetation in relatively undisturbed environments. A quasi-experimental situation exists in Rocky Mountain National Park, where elk Cervus elaphus populations have increased 3-fold since 1968 following their release from artificial controls within the park. We reviewed data collected on vegetation transects monitored over the 25-year period, 1968-1992. Data were subjected to rigorous statistical analysis to detect trends following the release of elk from artificial controls. Increases in elk habitat use and decreases in deer habitat use were observed. Significant increases in cover of mosses and lichens occurred in three of four vegetation types. Percent cover of bare ground, forbs Selaginella densa and Carex spp. increased on grassland transects. Increases in timothy Phleum pratense were observed on meadow transects. Graminoid and litter cover increased on sagebrush transects, and shrub cover and litter cover increased on bitterbrush transects. Some grazing induced responses were detected. Grazing resistant species such as sedges native, timothy exotic, and club mosses increased and the amount of bare ground increased on some grazed sites. Theamount of bare ground increase was minor 34, and grass and shrub cover increased in the shrub plots.