1. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau College of Forestry Northwest A&F University Yangling 712100 China
2. Department of Biological Sciences Macquarie University North Ryde NSW 2109 Australia
3. AXA Chair Programme in Biosphere and Climate Impacts Department of Life Sciences Imperial College London Silwood Park Campus Buckhurst Road Ascot SL5 7PY UK
4. United States Department of Agriculture – Agricultural Research Service Robert W. Holley Centre for Agriculture and Health Ithaca NY 14853 USA
5. Earth Sciences Division Lawrence Berkeley National Laboratory 1 Cyclotron Road Berkeley CA 94720 USA
6. Department of Biological Sciences Institute of Environmental Sciences University of Quebec at Montreal C.P. 8888 Succ. Centre‐Ville Montréal H3C 3P8 QC Canada