Willamette Valley oak woodlands, savannas, and prairies persist on only a fraction of their original expanse. As a result of colonial land management practices, oak and prairie landscapes have largely been converted to other land uses. Possibly contributing to their degradation are the decline of grazing pressure from native ungulate species and strategic burning practices by Indigenous peoples, which creates greater opportunities for shrub encroachment and dominance of nonnative plant species. In this study, we compared the impacts of short-duration targeted goat and sheep herbivory, mowing, and burning for restoring native vegetation and controlling overgrown shrubs on Tribal lands in the Willamette Valley. Changes to plant community structure and composition were assessed. All strategies resulted in some shrub cover reduction and increase in native perennial forb cover. Response to treatments varied depending on the shrub genus. Targeted herbivory had the least meaningful changes of any treatment. Mowing yielded the most dramatic reduction in shrub cover along with a small increase in annual grass cover. Burning caused a slight setback to annual grass cover while increasing native perennial cover more than other treatments. In the discussion, we also share qualitative observations and practical considerations about targeted herbivory. We hope our project will contribute to the adaptive management toolkit for Pacific Northwest oak and prairie land stewards.
Cascadia Prairie-Oak Partnership
Providing coordination for the technical prairie community in the Willamette Valley, Puget Trough, Georgia Basin (WPG) ecoregion and beyond.