1. Department of Botany, University of Wisconsin-Madison, 430 Lincoln Drive, Madison, WI 53706, U.S.A.
2. USDA Forest Service, Portland Forestry Sciences Lab, 620 SW Main, Suite 400, Portland, OR 97205, U.S.A.
3. Western Arctic National Parklands, National Park Service, 41A Wandling Road, Winthrop, WA 98862, U.S.A.
4. Department of Ecosystem Science & Management, The Pennsylvania State University, 207 Forest Resources Building, University Park, PA 16802, U.S.A.
5. Biology Department, Boise State University, Boise, ID 83642, U.S.A.