1. Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
2. Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan
3. Forestry & Forest Products Research Institute, Tsukuba, Japan
4. Gakuden residence #A-3, 4-1-1, Kita, Odori, Engaru-chou, Monbetsu-gun, Japan