aCollege of Geography and Environment, Shandong Normal University, 88 Wenhua Donglu, Jinan 250014, Shandong, China, Tel. +86 531 86182550; Fax: +86 531 86180107; emails: kongqiang0531@hotmail.com (Q. Kong), xufeisdnu@yahoo.com (F. Xu), mailxsg@126.com (S. Xu), 392331698@qq.com (Y. Du), qianwang86@sdnu.edu.cn (Q. Wang) bNo. 4 Middle School of Ningyang County, 118 Xinggang Road, Tai’an 271400, Shandong, China, email: 1737197806@qq.com cSchool of Engineering, RMIT University, 402 Swanston Street, Melbourne, VIC 3000 Australia, email: li.shu846@gmail.com dCollege of Life Science, Shandong Normal University, 88 Wenhua Donglu, Jinan 250014, Shandong, China, emails: mingshengmiao@163.com (M. Miao), 373400619@qq.com (Q. Liu), 2410191093@qq.com (S. Ma)