Fire exclusion effects on riparian forest dynamics in southwestern Oregon

Euro-American settlement and organized fire suppression have been associated with structural and compositional changes in many upland forests of the western United States, but little is known about the impacts on riparian forests, portions of the landscape protected for habitat and water quality. In this study, we used dendro-ecological methods to characterize the pre-settlement disturbance and tree recruitment processes of riparian forests in the Rogue River basin of southwestern Oregon and to identify changes to the forest structure and composition post-settlement. Our results suggest riparian forests in our study area developed with frequent disturbance by fire and that Euro-American land management shifted these forests onto a new successional trajectory. Our findings indicate the current hands-off management regime for riparian forests under the Northwest Forest Plan will continue along this altered trajectory and have ecologically undesirable consequences. We suggest that the restoration of pre-settlement forest dynamics in fire-prone forests of southwestern Oregon will be most effective where it includes density reductions in overstory trees and prescribed fire in both upland and riparian forests.

► Examined effects of Euro-American settlement and fire suppression on riparian forests, SW Oregon.
► We found riparian forests in SW Oregon developed with frequent disturbance by fire.
► Euro-American land management shifted riparian forests to new successional trajectory.
► Under current policy, riparian forests continue altered trajectory with undesirable results.
► Suggest restoration of historical forest dynamics include overstory tree reduction with Rx fire.