1. University of California, Berkeley, CA 94720, USA.
2. University of Washington, Seattle, WA 98195, USA.
3. Northern Arizona University, Flagstaff, AZ 86011, USA.
4. U.S. Department of Agriculture Forest Service, Pacific Southwest Research Station, Davis, CA 95618, USA.
5. Colorado State University, Fort Collins, CO 80523, USA.
6. University of Arizona, Tucson, AZ 85721, USA.
7. University of Wisconsin, Madison, WI 53706, USA.