1. Department of Physical Geography, Faculty of Geosciences; Utrecht University; Heidelberglaan 2; 3508 TC; Utrecht; The Netherlands
2. Institute of Plant Sciences and Oeschger Centre for Climate Change Research; University of Bern; Altenbergrain 21; CH-3013; Bern; Switzerland
3. Department of Earth Sciences, Faculty of Earth and Life Sciences; Vrije Universiteit; De Boelelaan 1085; 1081 HV; Amsterdam; The Netherlands