1. Faculty of Agriculture; Utsunomiya University; 350 Mine-machi, Utsunomiya Tochigi, 321-8505 Japan
2. Graduate School of Agriculture; Utsunomiya University; 350 Mine-machi, Utsunomiya Tochigi, 321-8505 Japan
3. Division of Environmental Resources, Graduate School of Agriculture; Hokkaido University; Kita-ku, Sapporo, Hokkaido 060-8589 Japan
4. Faculty of Agriculture; Ehime University; 3-5-7 Tarumi, Matsuyama, Ehime 790-8566 Japan
5. Field Science Centre for Northern Biosphere, Forest Research Station; Hokkaido University; Kita-ku, Sapporo, Hokkaido 060-0809 Japan
6. Utsunomiya University Forests, Faculty of Agriculture; Utsunomiya University; 7556 Funyu, Shioya, Tochigi 329-2441 Japan