1. Key Laboratory of Mountain Surface Processes and Ecological Regulation; Institute of Mountain Hazards and Environment; Chinese Academy of Sciences; No. 9, Block 4 South Renmin Rd. 610041 Chengdu China
2. Department of Renewable Resources; University of Alberta; 442 Earth Sciences Building Edmonton AB T6G 2E3 Canada
3. Canadian Forest Service; Northern Forestry Centre; 5320 122nd St. Edmonton AB T6H 3S5 Canada