Russell L Scott, Agricultural Research Service Tucson, Tucson, AZ, United States, John F Knowles, USDA-ARS, Southwest Watershed Research Center, Tucson, AZ, United States, Jacob A Nelson, Max Planck Institute for Biogeochemistry, Jena, Germany, Xi Li, Peking University, Beijing, China, Pierre Gentine, Department of Earth and Environmental Engineering, Columbia University, New York, NY, United States and Joel A Biederman, University of Arizona, Tucson, AZ, United States