Alterations to riparian vegetation resulting from beaver pond life histories.

摘要

This thesis explores the ways in which vegetation dynamics are affected by beavers (Castor canadensis) in the Pole Mountain Recreation Area of the Medicine Bow National Forest, southeast Wyoming. Previous beaver-related research in this area focused on inventorying beaver pond counts, examining vegetation cycles associated with beaver ponds, and determining the carrying capacity of beavers based on vegetation availability. My research investigated the impacts to riparian vegetation resulting from beaver ponds being established or lost and how riparian zones responded to extended periods without beaver activity. I developed new methods to use a laser rangefinder to accurately conduct field surveys and classify landcover at a 1 meter spatial resolution from National Agriculture Imagery Program data. My results show that the establishment of a beaver pond eliminates aspen (Populous tremuloides) within 80-meters of a pond and drastically increases willow abundance in the same area. When a beaver pond is lost, vegetation composition surrounding the lost pond rapidly returns to a non-beaver state through the conversion of willow (Salix spp.) to aspen and conifer. Vegetation composition in beaver influenced areas can be altered in as little as 8 years. This relatively short length required for vegetation to change will allow managers to alter beaver management strategies for desired vegetation outcomes.