This research was sponsored by the National Natural Sciences Foundation of China,Hunan Provincial Natural Science Foundation of China,Program for New Century Excellent Talents in University,China Postdoctoral Science Foundation,the program of Hunan Provincial Science and Technology Plans,by the Hunan Provincial Program for Development of Key Disciplines in Ecology
supported by the National Natural Science Foundation of China (31071885,30970325,31093430);in part by the Program of Ministry of Science and Technology of the Republic of China(2012FY110803) to Dr.ZHANG Feng