1. Department of Ecology, College of Urban and Environmental Science; Peking University; Beijing China
2. LSCE, UMR1572, CEA, CNRS; Gif-sur-Yvette France
3. Laboratoire de Biogéochimie Isotopique; Thiverval-Grignon France
4. Department of Environmental Studies; University of California; Santa Cruz California USA
5. Max Planck Institute for Biogeochemistry; Jena Germany