Natural Regeneration and Influencing Factors of Castanopsis orthacantha Evergreen Broad-leaved Forest in Central Yunnan

Using a Castanopsis orthacantha forest located in central Yunnan, the entropy method was used to comprehensively evaluate the forest regeneration effect, and Pearson correlation analysis and path analysis model were established to study the influencing factors of understory regeneration. The results showed that among the 26 evergreen broad-leaved forest plots, 10 plots had a regeneration index of more than 0.6, accounting for 38.5 %. The effect of natural regeneration in the forest was general, however the regenerated tree species were relatively rich, a total of 18 species, belonging to 9 families, and 15 genera. The forest was in a slow, natural restoration stage of positive succession. Soil porosity(r = 0.848, P < 0.01) and water content(r = 0.855, P < 0.01) were significant factors affecting seedling(sapling) regeneration. Tree density and litter accumulation had dual effects on the understory regeneration of the C. orthacantha forest. The direct and indirect effects of stand number density on regeneration index were 0.002 and −0.11, respectively. The direct and indirect effects of litter accumulation on regeneration index were −0.238 and 0.219 respectively. The influence of each factor on the regeneration index was: soil porosity(0.856) > soil water content(0.461) > shrub coverage(0.361) > tree density(−0.108) > litter accumulation(−0.018). In the follow-up management, the natural regeneration of C. orthacantha evergreen broad-leaved forest can be promoted by artificial thinning, proper cleaning of litter, and improvement of soil conditions. This realizes the stability and sustainable management of C. orthacantha evergreen broad-leaved forest ecosystem.