1. Department of Microbial Ecology, Ecology Building, Lund University, SE‐223 62 Lund, Sweden;
2. Present address: Microbial Ecology, Groningen University, Biological Center, PO Box 14, 9750AA, Haren, the Netherlands;
3. Soil and Land Systems, School of Earth and Environmental Sciences and Centre for Soil–Plant Interactions, Waite Campus, University of Adelaide, Glen Osmond, South Australia 5064, Australia;
4. Present address: Department of Land, Air & Water Resources, University of California, Davis, One Shields Avenue, Davis, CA 95616‐8627, USA