2.1 Study area description
The study was conducted in Luoxi Town, Taihe County, Jiangxi Province, China (114.47′41.55″E, 26°51′14.73″N). This site has a subtropical monsoon humid climate with mean annual precipitation of 1438 mm, mean annual temperature of 18.9 ℃ and mean annual relative humid of 79 % (http://data.envbox.net/). The soil is red soil developed from a quaternary red clay, characterized with almost no humid layer and full of gravel on the surface due to water erosion. Masson pine, an evergreen coniferous tree, is an important species for timber production in southern China and its rosin is also one of the most important chemical raw materials. In addition, this species has become an excellent pioneer tree species for afforestation of barren hills in China, due to its resistance to drought and barrenness and strong adaptability. Consequently, aerial seeding of Masson pine has been widely established in southern China to limit the intensive soil erosion and accelerate the restoration of forest vegetation (Xiaoet al. 2015).