HABITAT ASSOCIATIONS OF CALIFORNIA RED-BACKED VOLES IN YOUNG AND OLD-GROWTH FORESTS IN WESTERN OREGON

Because of the reduction of old-growth forests in the Pacific Northwes t, and the controversy over timber management practices, patterns of a nimal abundance in young and old forests have gained attention. Result s from previous studies on California red-backed voles (Clethrionomys californicus), however, have been inconsistent; unmanaged young stands were reported to have similar abundance of California red-backed vole s as old-growth stands, while other studies suggested that numbers are higher in older stands. We compared California red-backed vole abunda nce in 5 young (30-60 yr old) and 5 old-growth (> 400 yr old) Douglas- fir (Pseudotsuga menziesii) stands in the central Oregon Cascade Range during spring 1988-1991. The average number of California redbacked v oles captured was consistently higher in old-growth stands (XBAR +/- S E, 8.4 +/- 1.9) than in young stands (2.0 +/- 0.8) during the 4 years of the study; 80% of the voles captured in the 5 young stands were fro m one unmanaged, fire regenerated stand. Our results support hypothese s of lower abundance of California red-backed voles in managed young f orests than in unmanaged older forests. Providing components of old-gr owth forests, such as deep organic-soil depths, residual large trees a nd snags, and coarse woody-debris in managed young stands will likely increase their potential as suitable habitat for California red-backed voles.