1. Forest Ecosystem Dynamics Group, Shikoku Research Center, Forestry and Forest Products Research Institute (FFPRI), 2–915 Asakura-nishimachi, Kochi, Kochi 780-8077, Japan
2. Soil-Plant Ecosystem Group, Hokkaido Research Center, FFPRI, 7 Hitsujigaoka, Toyohira, Sapporo, Hokkaido 062-8516, Japan
3. Kyushu Research Center, FFPRI, 4-11-16 Kurokami, Kumamoto, Kumamoto 860-0862, Japan
4. Department of Forest Site Environment, FFPRI, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan