Gap formation features of humid evergreen broad-leaved forest in central subtropical Wawushan Mountain,Sichuan Province,China Tree Regeneration in an Abies fargesii-Betula utilis Mixed Forest and Effects of the Soil Chemical Properties on Regeneration Impact of logging intensity on the spatial distribution and association of dominant tree species in a broadleaved Korean pine mixed forest Characteristics of Soil Seed Bank and Tree Regenerations of Riparian Forests in the Upper Reach of Wenyuhe Watershed in Shanxi Province