1. Geobotany, Faculty of Geography and Geosciences, University of Trier, Behringstraße 21, 54296 Trier, Germany
2. Department of Geography, Kenyatta University, P.O. Box 43844, GPO 00100 Nairobi, Kenya
3. Soil Science, Faculty of Geography and Geosciences, University of Trier, Behringstraße 21, 54296 Trier, Germany