1. W. K. Kellogg Biological Station and Department of Crop and Soil Sciences, Michigan State University, Hickory Corners, MI 49060, USA.
2. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6036, USA.
3. Department of Agricultural Economics, Purdue University, West Lafayette, IN 47907, USA.
4. Center for Environmental Studies, Brown University, Providence, RI 02906, and Environmental Defense Fund, Boston, MA 01028, USA.
5. The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA.
6. Natural Resources and Environmental Sciences, University of Illinois, Urbana, IL 61801, USA.
7. Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO 80523-1499, USA.
8. Pasture Systems and Watershed Management Research Unit, U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS), University Park, PA 16802, USA.
9. Department of Plant Sciences, University of California, Davis, CA 95616, USA.
10. Department of Agronomy, Iowa State University, Ames, IA 50011, USA.
11. Ecological Society of America, Washington, DC 20036, USA.
12. National Institute for Research in the Amazon (INPA), Manaus, Amazonas, CEP 69011-970, Brazil.
13. Soil Plant Nutrient Research, USDA-ARS, Fort Collins, CO 80526-8119, USA.
14. Center for Sustainability and the Global Environment (SAGE), Nelson Institute for Environmental Studies, University of Wisconsin-Madison, Madison, WI 53726, USA.
15. Instituto de Eletrotécnica e Energia, University of Säo Paulo, Säo Paulo, Brazil.
16. Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, WI 53706, USA.
17. The H. John Heinz Center for Science, Economics, and the Environment, Washington, DC 20006, USA.
18. Department of Botany, Oklahoma State University, Stillwater, OK 74078, USA.
19. Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR 72701, USA.
20. Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USA.
21. Cary Institute of Ecosystem Studies, Millbrook, NY 12545, USA.
22. PRBO Conservation Science, Petaluma, CA 94954, USA.
23. USDA-ARS, University of Nebraska, Lincoln, NE 68583, USA.