1. Department of Environmental Chemistry, University of Kassel, Nordbahnhofstraße 1a, 37213 Witzenhausen, Germany
2. Institute of Silviculture, University of Freiburg, Tennenbacherstr. 4, 79106 Freiburg i. Br., Germany
3. Institute of Soil Science and Forest Nutrition, University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany