1. Center for Global Environmental Research; National Institute for Environmental Studies; 16-2 Onogawa Tsukuba 305-8506 Japan
2. Graduate School of Life Sciences; Tohoku University; Aoba Sendai 980-8578 Japan
3. CREST; Japan Science and Technology; Chiyoda Tokyo 102-0076 Japan
4. Center for Crop System Analysis; Wageningen University; PO Box 430 6700 AK Wageningen The Netherlands
5. Graduate School of Life and Environmental Sciences; University of Tsukuba; 1-1-1 Tennodai Tsukuba Ibaraki 305-8572 Japan