1. Department of Silviculture & Forest Ecology of the Temperate Zones, University of Göttingen, Büsgenweg 1, D-37077 Göttingen, Germany.
2. Energieagentur Region Göttingen e.V, Berliner Str. 2, D-37073 Göttingen, Germany.
3. Faculty of Science and Technology, Free University of Bozen-Bolzano, Piazza Università 5, I-39100 Bolzano, Italy.