ACKNOWLEDGEMENTS
This study was supported by the Second Tibetan Plateau Scientific Expedition and Research Program grant 2019QZKK0502 (HS), the Key Projects of the Joint Fund of the National Natural Science Foundation of China grant U1802232 (HS), the Yunnan Applied Basic Research Project grant 202001AT070060 (JGC), the National Natural Science Foundation of China grant 31271552 (JGC), the CAS ”Light of West China” Program (JGC), and the Young Academic and Technical Leader Raising Foundation of Yunnan Province grant 202205AC160053 (JGC). We are deeply grateful for Bradley J. Butterfield and Hong Qian for their constructive suggestions for improving the manuscript. We also thank Minshu Song, Zhichao Wu, Zijue Ren, Wenhan Liu, Wensheng Li and Shuliang Yu for their assistance with the field and laboratory experiments. Content determination of nutrient and stable isotope of cushion leaves were accomplished by Institutional Center for Shared Technologies and Facilities of XTBG, CAS.