Fig. 1

The distribution of districts and counties in Chongqing, China and its location. The study site is Chongqing, which is located in southwest of China, lying between latitude 28°10′-32°13′ N and longitude 105°11′-110°11′ E. The maps depicted in Fig. 1 were taken from National Geomatics Center of China. (http://www.ngcc.cn/ngcc/)