1. Max-Planck-Institute for Biogeochemistry, Postfach 10 01 64, D-07701 Jena, Germany.
2. The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA.
3. U.S. Geological Survey, Alaska Cooperative Fish and Wildlife Research Unit, University of Alaska, Fairbanks, AK 99775–7020, USA.
4. National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307–3000, USA.
5. University of Montana, Missoula, MT 59812, USA.
6. NREL, Colorado State University, Fort Collins, CO 80523–1499, USA.
7. Plant Ecology, Lund University, Ekologihuset 223 62 Lund, Sweden.
8. U.S. Department of Agriculture, Forest Service, Oregon State University, Forest Science Laboratory, 3200 Southwest Jefferson Way, Corvallis, OR 97333, USA.
9. Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22903, USA.