1. School of Forestry, Northern Arizona University, Flagstaff, AZ 86001, USA.
2. U.S. Geological Survey, Southwest Biological Science Center, Flagstaff, AZ 86001, USA.
3. USDA Forest Service, Rocky Mountain Research Station, Missoula, MT 59801, USA.
4. USDA Forest Service, Rocky Mountain Research Station, Forest and Woodland Ecosystems Science, Flagstaff, AZ 86001, USA.