1. School of Geography, South China Normal University; Zhongshan West Avenue No. 55 510631 Guangzhou China
2. Institute of Geography, University of Cologne, Albertus-Magnus-Platz; 50923 Köln Germany
3. Institute of Geography and Geology; Ernst Moritz Arndt University Greifswald, Makarenkostr. 22 17487 Greifswald Germany