1. Karst Dynamics Laboratory, Ministry of Land and Resources, 40 Qixing Road, Guilin 541004, China.
2. Department of Geology and Geophysics, University of Minnesota, Twin Cities, MN 55455, USA.
3. College of Geography Science, Nanjing Normal University, Nanjing 210097, China.
4. Department of Geoscience, University of Iowa, Iowa City, IA 52242, USA.
5. State Key Lab of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710075, China.