1. a Pacific Northwest Research Station , USDA Forest Service , Corvallis, Oregon, USA
2. b Department of Forest Resources , Oregon State University , Corvallis, Oregon, USA
3. c Department of Forest Products , Swedish University of Agricultural Sciences (SLU) , Box 7060, Uppsala, SE-75652, Sweden
4. d Department of Forest Resource Management , Swedish University of Agricultural Sciences (SLU) , Umeå, Sweden