**Acknowledgements**

The authors would like to thank all the students and staff (Fangfang Qiang, Weijun Zhao, Huan Ma, Xingkai Zhao, Wei Qin, Zongkai Wu, Guangliang Liu, and Rui Xie) who helped in the field sampling process, especially Wu Qi Forestry Bureau.

We also thank the Engineering Research Center of Forestry Ecological Engineering, Ministry of Education, Beijing Forestry University. This study was supported by the 13th 5-year National Key Research and Development Program of China (No. 2016YFC0501602 & No. 2016YFC0501705).
