1. Rocky Mountain Research Station; USDA Forest Service; Fort Collins; CO 80526; USA
2. Department of Ecology; Swedish University of Agricultural Sciences; Uppsala 750 07; Sweden
3. Natural Resource Ecology Laboratory; Department of Ecosystem Science and Sustainability; Colorado State University; Fort Collins; CO 80523-1499; USA
4. Woods Hole Research Center; Falmouth; MA 02540-1644; USA
5. Department of Natural Resources and Environment; the University of New Hampshire; Durham; NH 03824; USA
6. Pacific SW Research Station; Institute of Pacific Islands Forestry; USDA Forest Service; Hilo; HI 96785; USA
7. Department of Earth System Science; University of California; Irvine; CA 92697-3100; USA
8. Landcare Research; Palmerston North 4442; New Zealand
9. Agroscope Reckenholz Tanikon; Air Pollution Climate Group; Zurich 8046; Switzerland
10. School of Forestry and Environmental Studies; Yale University; New Haven; CT 06511; USA