1. Max-Planck-Institute for Biogeochemistry; 07701 Jena Germany
2. Institute of Biology; University of Leipzig; 04103 Leipzig Germany
3. Institute for Geosciences; Friedrich-Schiller-University Jena; 07749 Jena Germany
4. International Max Planck Research School on Earth System Modelling; 20146 Hamburg Germany
5. Institute of Geography and Geoecology; Karlsruhe Institute of Technology (KIT); 76131 Karlsruhe Germany
6. Department of Geography; University of Wisconsin; Madison WI 53706 USA