1. Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, Japan
2. Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
3. Faculty of Agriculture, University of the Ryukyus, Okinawa, Japan
4. National Agriculture and Food Research Organization, Tohoku Agricultural Research Center, Agricultural Radiation Research Center, Fukushima, Japan
5. Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan
6. Institute of Soil Science and Land Evaluation, Soil Biology Department, University of Hohenheim, Stuttgart, Germany