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UBC Theses and Dissertations

Aspen, elk, and fire in the Canadian Rocky Mountains White, Cliff


Trembling aspen (Populus tremuloides) is failing to survive through the sapling stage (2 to 4 m) to tree size in many national parks in western North America. Hypotheses for aspen decline include reduced burning, climate change, high herbivory by native ungulates (mainly elk (Cervus elaphus)), or interactions between these factors. Historic and current aspen condition was investigated in several watersheds, inside and outside of national parks, in the Rocky Mountains of Alberta, Canada to determine the causes of aspen decline. Methods included repeats of historical photographs, fire history by dendrochronology, time-series analysis (of climate, burned area, elk density, and aspen regeneration), wildlife exclosure measurements, analysis of elk functional herbivory response to aspen density, and effects of predation risk on elk-aspen foraging patterns. Aspen regeneration was abundant in historic photographs, is currently abundant in areas with low elk density (

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