基金We are grateful to Da-Wen Li and Ailaoshan Station for Subtropical Forest Ecosystem Studies, Chinese Academy of Sciences for field assistance. This work was supported by the National Natural Science Foundation of China (31100410, 31470575 and 30830027), the National Key Technology R&D Program of China (2011BAD30B00), and Chinese Academy Science 135 Program (XTBG-T01, F01).