Acknowledgements

This work was supported by National Key Research Program of China (2016YFC0500700), National Natural Science Foundation of China (31602004, 41230852, 31601987, 41601586, 41601053), Deployment Program of the Chinese Academy of Sciences (KJZD-EW-TZ-G10) and Technical System of Modern Forage Industry of the Ministry of Agriculture (CARS-35- 40). We thank Weijun Li, Xiuyun Ji and the management bureau of Yunwushan Grassland Natural Reserve for their help with the field experiments.
