1. Plant Ecology Research Laboratory PERL, School of Architecture, Civil and Environmental Engineering, EPFL , CH-1015 Lausanne , Switzerland
2. Forest Dynamics Research Unit, Swiss Federal Institute for Forest, Snow and Landscape WSL , CH-8903 Birmensdorf , Switzerland
3. Institute of Agricultural Sciences, ETH Zurich , CH-8092 Zurich , Switzerland
4. Institute of Terrestrial Ecosystems, ETH Zurich , CH-8092 Zurich , Switzerland
5. Community Ecology Unit, Swiss Federal Institute for Forest, Snow and Landscape WSL , CH-1015 Lausanne , Switzerland