1. Department of Forest Resources; University of Minnesota; St. Paul MN 55108 USA
2. USDA Forest Service; Northern Research Station; Grand Rapids MN 55744 USA
3. The Rubenstein School of Environment and Natural Resources; University of Vermont; Burlington VT 05405 USA
4. U.S. Geological Survey; Southwest Biological Science Center; Flagstaff AZ 86001 USA
5. School of Forest Resources; University of Maine; Orono ME 04469 USA
6. USDA Forest Service; Rocky Mountain Research Station; Fort Collins CO 80526 USA