1. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
2. Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China
3. Department of Chemistry and Biochemistry
4. Howard Hughes Medical Institute, University of Colorado, Boulder, CO 80309, USA.