Acknowledgments
We are grateful to Katja Steininger, Ute Petersen, Elke Tietz, H. Fleischmann, and the land owners for their assistance in carrying out the fieldwork. We also thank Stefan Mecke and Antonia Ortmann for their assistance with GIS analysis. The authors are grateful to P. Michels for proving valuable comments and suggestions on the manuscript language. This study was funded by a research Grant (Grant No. 91563454) from the German Academic Exchange Service (Deutscher Akademischer Austauschdienst , DAAD) to the corresponding author.