1. School of Forest Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
2. Forest Ecology, Institute of Terrestrial Ecosystems, Department of Environmental Systems Science, ETH Zurich. Universitätstrasse, 16, 8092 Zurich, Switzerland
3. University of Natural Resources and Life Sciences (BOKU) Vienna. Peter-Jordan Straβe 82, 1190 Vienna, Austria