1 Department of General Geography/Human-Environment Research, Institute of Geography, University of Wuppertal, 42119 Wuppertal, Germany. Electronic address: jheil@uni-wuppertal.de.
2 Department of Soil Science/Soil Ecology, Institute of Geography, Ruhr-University Bochum, 44780 Bochum, Germany.
3 Department of General Geography/Human-Environment Research, Institute of Geography, University of Wuppertal, 42119 Wuppertal, Germany.