Temporal Changes in Community Structure over a 5-Year Successional Stage in a Subtropical Forest

In the context of global warming, the changes of forest structure, diversity, and productivity along with forest succession have always been a topic of interest for many researchers. Studying the changes in community structure, biomass, and diversity of different diameter at breast height (DBH) classes in subtropical mountainous forests during forest succession can provide data in support of future forest succession predictions and forest management. We analyzed the changes of three DBH classes in a 10-ha plot while studying subtropical mountainous forest succession in 2012 and 2017. The results showed that during forest succession, the community abundance and richness significantly decreased while biomass increased slightly. Among the three DBH classes, changes were the greatest in small trees, followed by large trees, and then medium-sized trees. The abundance, biomass, richness, and Shannon-Wiener index of small trees all decreased significantly. In forests with medium-sized trees, biomass decreased significantly and abundance did not change significantly. In large trees, abundance and biomass increased significantly. Changes were observed in environmental driving factors during forest succession. In 2012, driving factors with significant effects included total phosphorus, transmitted direct solar radiation, organic matter, and capillary water capacity. In 2017, two driving factors were total phosphorus and total potassium while the main driving factor was still total phosphorus. The results showed that during forest succession the abundance and diversity of small trees were principal components of community abundance and diversity. A reduction in small-tree abundance and diversity will decrease community abundance and diversity. Large-tree biomass was a principal component of community biomass; accumulation of large-tree biomass will increase community biomass. Schima superba Gardner and Champ. and Castanopsis carlesii (Hemsl.) Hayata are the main dominant species in this area, which can quickly form stable communities. S. superba is also a fire-resistant tree species. Therefore, in natural forest management, planting of S. superba and C. carlesii in the secondary bare land can be considered. In addition, the evergreen broad-leaved forest can be recovered to the forest structure and productivity level before selective cutting, which provides important inspiration for forest management in the region.