1. University of Washington, Department of Biology, Box 351800, Seattle, WA 98195, USA.
2. USDA Forest Service, Pacific Northwest Research Station, 3625 93rd Ave. SW, Olympia, WA 98512, USA.
3. University of Washington, School of Environmental and Forest Sciences, Box 352100, Seattle, WA 98195, USA.
4. University of Montana, Department of Forest Management, 32 Campus Drive, Missoula, MT 59812, USA.