Acknowledgments
We thank Ting-Ting Shen, Yu-Xin Wang, Feng-Miao Zhao for continuously collecting data in the field and for the laboratory analysis during the study period. We thank the Key Laboratory of Grassland Resources of the Ministry of Education (Inner Mongolia Agricultural University) for their support, and also thank anonymous referees for their constructive comments that significantly. This study was financially supported by High-Level Talent Research Project of Inner Mongolia Agricultural University (NDYB2020-5), National Natural Science Foundation of China (32192463).