湖南省林业科技创新专项资金XLK201432;湖南省科技计划项目2014FJ3126;衡阳市社会科学基金2014D100;衡阳市科学技术发展计划项目2014KJ27;grants from the Special Foundation of Forestry Science and Technology Innovation of HunanXLK201432;the Science and Technology Project of Hunan Province2014FJ3126;the Social Science Foundation of Hengyang2014D100;Science and Technology Development Project of Hengyang City2014KJ27