1. CAS Key Laboratory of Forest Ecology and Management; Institute of Applied Ecology; Chinese Academy of Sciences; Shenyang 110164 China
2. Key Laboratory of Grassland Resources, Ministry of Education; College of Grassland, Resources and Environment; Inner Mongolia Agricultural University; Hohhot 010018 China
3. Department of Ecology, Evolution and Behavior; University of Minnesota; St. Paul Minnesota 55108 USA
4. State Key Laboratory of Vegetation and Environmental Change; Institute of Botany; Chinese Academy of Sciences; Xiangshan Beijing 100093 China
5. Key Laboratory of Plant Stress Biology; College of Life Sciences; Henan University; Kaifeng Henan 475004 China