1. Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), SE‐901 83 Umeå, Sweden
2. Departamento de Ecología y Biología Animal, Universidad de Vigo, 36310 Vigo, Spain
3. Centre for Ecology and Hydrology, Lancaster Environment Centre, Lancaster LA1 4AP, UK
4. Department of Plant Physiology and Umeå Plant Science Centre, University of Umeå, SE‐901 87 Umeå, Sweden
5. Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen AB15 8QH, UK
6. Southern Swedish Forest Research Centre, SLU, PO Box 49, SE‐230 53 Alnarp, Sweden