PS 72-113 - Restoring fire regimes of southwestern Oregon: Density and species composition of a forested landscape

Friday, August 11, 2017
Exhibit Hall, Oregon Convention Center
Kerry L. Metlen, Southwest Oregon Field Office, The Nature Conservancy in Oregon, Medford, OR and Darren Borgias, The Nature Conservancy in Oregon

Landscape scale forest restoration thins out excess, small, shade tolerant trees and restores a more natural fire regime to increase forest adaptive capacity to a changing climate and resilience to fire. Mechanical treatments are informed by historical reference conditions, tempered to protect and preserve existing closed forest habitats, and guided by society’s needs and concerns. The Ashland Forest Resiliency Stewardship Project is doing this work in the mediterranean mixed conifer hardwood forests of southwestern Oregon. Multiparty monitoring, led by The Nature Conservancy, has been ongoing since 2010. Stand exam plots and cut tree tallies allow characterization of treated stands. We evaluate the extent to which the treatments have restored historical stand structure, and species composition relative to a locally derived reference data set based on 0.1-ha plots stratified across the project area (n=50) where we reconstructed forest species composition and structure back to the date of last widespread wildfire, 1910.


A mixture of non-commercial and commercial fuel reduction treatments was implemented on 5,960-ha of a 9,000-ha planning area, largely with objectives of maintaining canopy cover and suppressing ladder fuel regrowth. Commercial treatments were implemented on 1,140 ha but open forest restoration was only the focus on 869 ha. The most common commercial treatments reduced basal area from 51 m2/ha to 35 m2/ha, but in stands where open forest restoration was prioritized basal area was reduced from 43 m2/ha to 31 m2/ha. Reference data found significant increases in forest density in all settings and would suggest a target density of 18 m2/ha: substantially lower than even treatments where restoration was the primary objective. Historically, warm insolation sites were composed of 48% early seral tree species, significantly more than on insolation settings only where 17% of trees were early seral. Current data show that now 93% of the trees are late seral species, regardless of setting. Treatments primarily removed shade tolerant trees (95% of commercially cut trees) and shifted the species composition toward early seral tree species, from about 7% P. ponderosa to about 9% P. ponderosa. The Ashland Forest Resiliency project is making progress toward resilient forest conditions, but significant collaborative work remains to implement treatments that restore historically resilient forest density and species composition on even a small proportion of the landscape.