1. Institute of Desertification StudiesChinese Academy of Forestry Beijing 100091 PR China
2. Institute of Plant QuarantineChinese Academy of Inspection and Quarantine Beijing 100029 PR China
3. Department of Civil and EnvironmentPrinceton University Princeton NJ 08544 USA
4. Department of Climate and Space Sciences and EngineeringUniversity of Michigan Ann Arbor MI 48109 USA
5. Canadian Forest ServiceNatural Resources Canada 580 Booth Street Ottawa ON K1A 0E4 Canada
6. Environmental Sciences Division and Climate Change Science InstituteOak Ridge National Laboratory Oak Ridge TN 37831 USA