1. Soil Science of Temperate and Boreal Ecosystems, Buesgen Institute, University of Goettingen, Büsgenweg 2, 37077 Göttingen, Germany
2. Institute of Crop Science and Resource Conservation, Soil Science and Soil Ecology, University of Bonn, Nussallee 13, 53115 Bonn, Germany
3. now at: Department of Environmental Chemistry, University of Kassel, Nordbahnhofstraße 1a, 37213 Witzenhausen, Germany
4. Department of Geology, University of Cologne, Zülpicherstr. 49a, 50674 Cologne, Germany, now at: Department for Agroecosystem Research, University of Bayreuth, 95440 Bayreuth, Germany
5. Max‐Planck Institute for Biogeochemistry, P.O. Box 100164, 07701 Jena, Germany
6. Leibniz Laboratory for Radiometric Dating and Isotope Research, Christian Albrechts University of Kiel, Max‐Eyth‐Str. 11, 24118 Kiel, Germany, now at: Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
7. Max‐Planck Institute for Biogeochemistry, P.O. Box 100164, 07701 Jena, Germany, now at: University of California, Irvine, Department of Earth System Science, 2101 Croul Hall, Irvine, CA, 92697–3100, USA
8. Leibniz Laboratory for Radiometric Dating and Isotope Research, University of Kiel, Max‐Eyth‐Str. 11, 24118 Kiel, Germany