1. Department of Biology andWildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, USA;
2. The Ecosystems Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA o02543, USA;
3. U.S. Geological Survey, Alaska Cooperative Fish and Wildlife Research Unit, 214 Irving I Building, University of Alaska Fairbanks, Fairbanks, AK 99775, USA;
4. The Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA;
5. Ecosystem Dynamics and the Atmosphere, NCAR, PO Box 3000, Boulder, CO 80305, USA;
6. Department of Geography, Boston University, 675 Commonwealth Avenue, Boston, MA 02215, USA;
7. NASA Goddard Space Flight Center, Code 923, Greenbelt, MD 20771, USA;
8. Geophysical Institute, University of Alaska Fairbanks, AK 99775, USA;
9. U.S. Geological Survey, ms 962, Menlo Park, CA, USA