Relationship Between Occurrence of Laminated Root Rot and Site Characteristics in Douglas-Fir Forests of the Northern Oregon Coast Range
Abstract In the northern Oregon Coast Range 70- to 100-yr old Douglas-fir (Pseudotsuga menziesii) stands were evaluated to determine rate of infection by laminated root rot, caused by (Phellinus weirii), whether local disease occurrence was associated with site characteristics, and impacts of P. weirii on the number of trees and basal area. Overall infection rate was 5.6%, but varied from 0.0 to 14.7% among stands. There was a significant association between occurrence of P. weirii and slope position. The rate of infection on ridges, upper slopes, middle slopes, and lower slopes was 13.0, 7.3, 4.1, and 0.0%, respectively. Occurrence of P. weirii was independent of plant association and aspect. Infected plots contained 25% less live Douglas-fir basal area and 35% fewer live Douglas-fir trees per ac than uninfected plots. West. J. Appl. For. 9(1):14-17.