Conflict of interest
The authors declare that there are no conflicts of interest.
Acknowledgments
This research was financed by the Erich-Ritter and HerzogSellenberg
Foundations within the Stifterverband fu¨r die
Deutsche Wissenschaft (CUP n. I41J10000880007). We thank
He Ping and Xu Jie, Chinese Research Academy of Environmental
Sciences (CRAES) in Beijing, and the Zhangye
Environment Monitoring Center for logistic support in sampling.
The manuscript was professionally edited for language
by Joe Cirella.