1. Department of Environmental Technology and Department of Soil Ecology, UFZ-Helmholtz Centre for Environmental Research UFZ, Permoserstrasse 15, 04318 Leipzig, Germany; Department of Plant Physiology, RWTH Aachen University, Worringerweg 1, D-52074 Aachen, Germany; Department of Primary Production and Microbial Ecology, Leibniz-Centre for Agricultural Landscape and Land Use Research, D-15374 Muencheberg, Germany; and Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada