1. Department of Biology; Faculty of Science, Kyushu University; Fukuoka Japan
2. Graduate School of Life Sciences; Tohoku University; Sendai Japan
3. Graduate School of Life Science; Hokkaido University; Sapporo Japan
4. Hokkaido Research Center; Forestry and Forest Products Research Institute; Sapporo Japan
5. Department of Plant Ecology; Forestry and Forest Products Research Institute; Tsukuba Japan