Quaking aspen (Populus tremuloides) is an important tree species for watershed protection, wildlife, and biodiversity in the western United States. Aspen are uncommon in western Oregon, and little is known about their historic range or current condition in the region. This study will assess the impact herbivory and conifer encroachment are having on aspen stands in western Oregon on the Willamette National Forest. Mule deer (Odocoileus hemionus), black-tailed deer (Odocoileus hemionus Columbianus), and Roosevelt Elk (Cervus elaphus) all occur naturally on the National Forest of the study area.

I hypothesize that the aspen stands that are declining (not effectively recruiting smaller aspen into the overstory) are doing so because of conifer encroachment and herbivory. Specifically, my hypotheses are that

• Conifer encroachment is negatively associated with 1) young aspen density and 2) short-term and long-term aspen recruitment
• Herbivore-accessible aspen stands (non-refugia) have 1) lower mean height of young aspen, and 2) a gap in expected aspen age classes across time, when compared to stands that are not herbivore-accessible (refugia).
• Herbivory is negatively associated with 1) young aspen density, and 2) short-term and long-term aspen recruitment

I will determine whether herbivory or conifer encroachment are having an impact on the declining aspen stands, and if so, determine which one is having a greater impact.