1. Chengdu Institute of Biology; Chinese Academy of Sciences; PO Box 416 Chengdu 610041 China
2. Key Laboratory of Bio-resources and Eco-environment of Ministry of Education; College of Life Sciences; Sichuan University; Chengdu 610064 China
3. Mianyang Normal University; Mianyang 621000 China
4. Key Laboratory of Mountain Surface Processes and Ecological Regulation; Institute of Mountain Hazards and Environment; Chinese Academy of Sciences; Chengdu 610041 China
5. Department of Agricultural Sciences; University of Helsinki; PO Box 27 Helsinki FI-00014 Finland