Conifer bole utilization by wood-boring beetles in western Oregon

We studied wood excavation by scolytid and cerambycid beetles in decomposing boles of four conifer species duringthe first two years on the ground in western Oregon. Colonization density and gallery volumes were measured in experi-mental boles (0.5 m diameter x 5 m length) of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), western hemlock(Tsuga heterophylla (Raf.) Sarg.), Pacific silver fir (Abies amabilis (Dougl.) Forbes), and western red cedar ( Thujaplicata Donn). Ambrosia beetles (Coleoptera: Scolytidae) colonized boles only during the 1st year and were essentiallyrestricted to Douglas-fir and western hemlock (removing 0.2% of the sapwood volume). Bark beetles (Coleoptera:Scolytidae) colonized boles only in the 1st year, primarily in Douglas-fir and Pacific silver fir (removing 7-8% of thephloem surface area). Wood borers (Coleoptera: Cerambycidae) excavated an additional 2.3% of the phloem surfacearea of Pacific silver fir in the 1st year and continued to excavate all species except Douglas-fir during the 2nd year.Consequences for the decomposition process are discussed.