1. Department of Agricultural and Resource Economics, University of Maryland, Symons Hall, College Park, Maryland, USA 20742
2. Department of Resource Economics & Environmental Sociology, University of Alberta, 551 General Services Building, Edmonton, Alberta, Canada T6G 2H1
3. School of Economics, Lanzhou University, No. 222 South Tianshui Road, Lanzhou, Gansu, China 730000
4. Department of Wood Science, University of British Columbia, 4028 Forest Sciences Centre, Vancouver, British Columbia, Canada V6T 1Z4
5. Department of Renewable Resources, University of Alberta, 442 Earth Sciences Building, Edmonton, Alberta, Canada T6G 2E3