1. Plant Production Systems Group; Wageningen University; PO Box 430 NL-6700 AK Wageningen The Netherlands
2. Netherlands Environmental Assessment Agency; PO Box 303 NL-3720 AH Bilthoven The Netherlands
3. Institute of Crop Science and Resource Conservation; University of Bonn; Katzenburgweg 5 D-53115 Bonn Germany
4. Earth System Analysis, Potsdam Institute for Climate Impact Research (PIK); PO Box 60 12 03 D-14412 Potsdam Germany