Acknowledgements
We thank Xin Jing, Litong Chen, Kaoping Zhang and Ke Zhao for their assistance with the soil sampling and lab analyses. This work was supported by the National Program on Key Basic Research Project (grant number 2014CB954002), the Strategic Priority Research Program of the Chinese Academy of Sciences (grant number XDB15010101); National Natural Science Foundation of China (grant number 41701298); the Basic work of science and technology of Ministry of Science and Technology of China (grant number 2015FY110100) and the Jiangsu Agricultural Biodiversity Cultivation and Utilization Research Center(0270756100ZX).