1. Department of Biology, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan
2. Soil-Plant Ecosystem Group, Hokkaido Research Center, Forestry and Forest Products Research Institute, 7 Hitsujigaoka, Toyohira, Sapporo, Hokkaido 062-8516, Japan
3. Forest Ecology Group, Kansai Research Center, Forestry and Forest Products Research Institute, 68 Nagaikyutaroh, Momoyama-choh, Fushimi-ku, Kyoto, Kyoto 612-0855, Japan
4. Department of Biological Sciences, Graduate School of Science, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan