1. Department of Biogeochemistry; WSL; Swiss Federal Institute for Forest; Snow and Landscape Research; Zürcherstr. 111; 8903; Birmensdorf; Switzerland
2. Department of Geography; University of Zürich; Winterthurerstr. 190; 8057; Zürich; Switzerland
3. Department of Ecology and Evolutionary Biology; Cornell University; E215 Corson Hall; Ithaca NY; 14853; USA