Hong Yang1,2, Mingguo Ma1, Julian R Thompson3, Roger J Flower3. 1. Chongqing Key Laboratory of Karst Environment, School of Geographical Sciences, Southwest University, Chongqing, 400715, China. hongyanghy@gmail.com mmg@swu.edu.cn. 2. CEES, Department of Biosciences, University of Oslo, Blindern, 0316 Oslo, Norway. 3. Department of Geography, University College London, London WC1E 6BT, UK.