Abstract:Exploring the population dynamics and influencing factors of foundation species can help deepen our understanding of forest carbon cycling and source-sink transitions and provides a theoretical basis for forest conservation. This study used a 20 hm2 plot in lower subtropical evergreen broad-leaved forest in Dinghushan as the research platform. Based on the initial survey data, it was determined that the top three species with the highest importance values and total basal area were the foundation species of the plot: Castanopsis chinensis, Schima superba, and Engelhardia roxburghiana. The population dynamics characteristics were analyzed using important values, mortality rates, recruitment rates and diameter class structure. Subsequently, based on these population dynamics features, the patterns of survival and changes in neighbor density were examined through the analysis of neighbor effects. The results showed that the population dynamics of C. chinensis and E. roxburghiana remained stable, maintaining dominance in the plot community with low mortality and recruitment rates. Whereas the population of S. superba experienced a sharp decline in dominance due to a large number of individual deaths from 2010 to 2015. There were significant negative correlations between the survival of C. chinensis juveniles and the density of conspecific neighbors, indicating apparent intraspecific competition or negative density dependence. During periods of population stability for S. superba, the survival of adults had significant positive correlations with the density of conspecific neighbors, consistent with the habitat filtering hypothesis. During periods of extensive individual deaths within the S. superba population, the significant positive correlation between the survival of adults and conspecific neighbor density disappeared, replaced by a significant positive correlation with the density of heterospecific neighbors. It was suggested that S. superba survival was more likely in areas where heterospecific individuals were clustered nearby, supporting the heterospecific facilitation hypothesis. The survival dynamics of E. roxburghiana individuals were not mostly significantly related to neighbor density, indicating that the survival of E. roxburghiana is hardly influenced by neighbors. In summary, there were interspecific differences in the responses of dominant species to neighbors, and the same species adopts different strategies at different life history stages, which supported the co-action of environmental filtering and niche differentiation in the community, maintaining species diversity and the functionality and stability of the ecosystem.