1. Uryu Experimental Forest, Field Science Center for Northern Biosphere, Hokkaido University, Moshiri, Horokanai 074-0741, Japan
2. Shikoku Research Center, Forestry and Forest Products Research Institute, Kochi, Japan
3. Northern Development Office, Field Science Center for Northern Biosphere, Hokkaido University, Sapporo, Japan
4. Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
5. Tomakomai Experimental Forest, Field Science Center for Northern Biosphere, Hokkaido University, Tomakomai, Japan