鼎湖山南亚热带常绿阔叶林建群种种群动态与邻体效应研究

Studies on the Population Dynamics and Neighbor Effects of Foundation Species of Lower Subtropical Evergreen Broad-leaved Forest in Dinghushan

摘要:

探究建群种的种群动态变化规律及其影响因素有助于加深对森林碳循环和源汇转换的了解，并为森林保护提供理论依据。该文以鼎湖山南亚热带常绿阔叶林20 hm²固定监测样地的建群种锥栗(Castanopsis chinensis)、荷木(Schima superba)和黄杞(Engelhardia roxburghiana)为研究对象，利用重要值、死亡率、补员率、径级结构等分析其种群动态特点，进而根据种群动态特征，通过邻体效应分析其存活与邻体密度间的变化规律。结果表明，锥栗种群和黄杞种群动态稳定，在样地群落中保持优势地位，死亡率与补员率较低；荷木种群在2010—2015年间大量个体死亡，在样地群落中优势地位急剧下降。锥栗中树个体的存活与同种邻体密度存在显著的负相关关系，表现出明显的种内竞争或负密度制约现象；荷木在种群动态稳定时期，大树个体存活与同种邻体密度存在显著的正相关关系，符合生境过滤假说；荷木在种群个体大量死亡时期，大树个体存活与同种邻体密度的显著正相关关系消失，而与异种邻体密度存在显著的正相关关系，即周围的异种个体聚集的地方荷木存活的可能性大，符合异群保护假说；黄杞个体的存活动态与邻体密度关系大多不显著，表明黄杞的存活几乎不受邻体影响。建群种对邻体的响应具有种间差异，同一物种在不同生活史阶段也有不同策略，佐证了环境过滤与生态位分化共同作用于该群落，维持了物种的多样性和生态系统的功能与稳态。

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.