1. Forest Ecosystem Research Centre, Institute of Forest Botany, University of Göttingen, Büsgenweg 2, D‐37077 Göttingen, Germany
2. School of Agricultural and Forest Sciences, University of Wales Bangor, Bangor, Gwynedd LL57 2UW, UK
3. Institute of Biological Information Processing, Research Centre Jülich, D‐52425 Jülich, Germany
4. Forest Research Institute of Lower Saxony, Grätzelstr. 2, 37079 Göttingen, Germany
5. To whom correspondence should be addressed at: School of Agricultural and Forest Sciences, University of Wales Bangor, Bangor, Gwynedd LL57 2UW, UK. E‐mail: