Funding for this research was provided by:
Scientific Research Fund of Hunan Provincial Education Department (13C1139)
Research Foundation of Central South University of Forestry and Technology of China (QJ2012013A)
Natural Science Foundation of Hunan Province (2015JJ4090)
Received: 24 January 2018
Accepted: 25 April 2018
First Online: 16 May 2018
: The authors declare that they have no competing interests.