1. University of Amsterdam Institute for Biodiversity and Ecosystem Dynamics (IBED)—Earth Surface Science Science Park 904 NL-1098 XH Amsterdam The Netherlands
2. University of Helsinki Department of Forest Sciences Latokartanonkaari 7 FI-00014 Helsinki Finland
3. Technische Universität Dresden Institute of Soil Science and Site Ecology Pienner Straße 19 D-01737 Tharandt Germany