Implications of Thinning for Wildlife: Amphibians

Dede Olson, PNW Research Station, Corvallis, OR

The complexity of forestry practices in the western Pacific Northwest includes various mixtures of reserved lands or trees, clearcut harvests, and forest thinning prescriptions. These mixtures are evident at all spatial scales, stand-to-landscape. The effects of prescriptions thus should be considered relative to these various scales, taking into account both local and neighborhood effects, and the scales at which the response parameters operate. For amphibians, few studies have considered the effects of forest thinning. We have two projects addressing this knowledge gap. Our southwestern Oregon study is just beginning, but will look at the response to thinning by terrestrial amphibians and mollusks in the Siskiyou National Forest. In northwestern Oregon, coordinated with the Bureau of Land Management (Salem, Eugene, Roseburg, and Coos Bay Districts) and the Siuslaw National Forest, we are examining the effects of combined thinning (to 80 trees per acre, with leave islands and clearcut patches) and riparian buffer widths (20 to 480 ft) on stream, bank, and terrestrial amphibians. This study has a pre-treatment/post-treatment/control design at 12 sites, and we are now analyzing our post-treatment data. Preliminary results are highly variable. General assemblages have not been altered dramatically, but species-specific reach level effects show both increases and decreases in abundances.

Keywords: Density management, riparian buffer, amphibians.