1. a State Key Laboratory of Forest and Soil Ecology , Institute of Applied Ecology, Chinese Academy of Sciences , Shenyang , 110164 , PR China
2. b Graduate University of Chinese Academy of Sciences , Beijing , 100101 , PR China
3. c College of Management, Shenyang Jianzhu University , Shenyang , 110168 , PR China
4. d College of Tourism Management, Shenyang Normal University , Shenyang , 110034 , PR China