本文由国家林业局全国森林经营基础研究项目1692016-03和杨凌示范区科技推广能力提升项目2015-TS-29资助;This work was supported by the Basic Research Project of National Forest Management from the State Forestry Bureau 1692016-03 and the Project for Improving the Abilities of Science and Technology in Yangling Demonstration Zone 2015-TS-29.