This study was supported by the International S&T Cooperation
Program from the Ministry of Science and Technology of China (No.
2012DFA91530), Special Fund for Forestry Scientific Research in
the Public Interest (No. 201204204), Projects of International
Cooperation and Exchanges NSFC (41161140353, 91325302), the
1st Youth Excellent Talents Program of the Organization Department of the Central Committee of the CPC, the Fundamental
Research Funds for the Central Universities (TD-JC-2013-2), and
the NGI GBV Fund (H.P.H. Arp). We also thank Potsdam Institutes of
Climate Change Impacts (PIK) in Germany for supporting J. Liu’s
visits, and the University of Leeds for providing J. Liu a Cheney
Senior Fellowship. We thank Steve Carpenter from the University
of Wisconsin and Elena Bennett from McGill University for sharing
discussions through the preparation of the manuscript.