1. Environmental Studies Program, 6182 Steele Hall, Dartmouth College, Hanover, NH 03755, USA
2. Graduate Degree Program in Ecology and the Department of Forest Sciences, Colorado State University, Fort Collins CO, 80523, USA
3. Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607–7060, USA
4. Department of Forest Sciences and the Natural Resources Ecology Laboratory, Colorado State University, Fort Collins CO, 80523, USA
5. Department of Rangeland Ecosystem Sciences and the Natural Resources Ecology Laboratory, Colorado State University, Fort Collins CO, 80523, USA