关键词: 密度制约效应, 生活史阶段, 邻域分析, Janzen–Connell假说

Abstract: Aims Our aim is to explore density dependence in various life stages of temperate forests and determine the varying importance of density dependence across different life stages. To provide a theoretical foundation for species coexistence at a local scale in temperate forests. Methods Based on the retest data of trees and the dynamic monitoring data of 451 seedling monitoring quadrats in a 21.12 hm2 fixed monitoring plot of coniferous and broadleaved mixed forest in Jiaohe, Jilin Province for three consecutive years (2016–2018), four models were used to analyze the effects of density restriction on different life stages at two levels of community and species: basic generalized linear mixed model, interaction generalized linear mixed model, random effects generalized linear mixed model and individual random effects generalized linear mixed model. Important findings At the community level, conspecific neighborhood effect significantly affected the survival of all life stages. Conspecific adult tree neighbors exhibited significant negative impacts on seedling survival rate, while conspecific seedling neighbors had a positive impact on seedling survival rate. The survival of conspecific neighbors had a considerable negative impact on both the saplings and adult trees. Conspecific Negative Density Dependence (CNDD) decreases with the stages of life history. Heterospecific neighbor effects varied with neighbor radius and life stages, but there is no clear trend. At the species level, the significant variations of neighbor effects between species was detected only at the adult tree stage. On the other hand, no discernible variations were discovered across species in different life stages with regard to conspecific and heterospecific neighbor effects. Negative density dependence is present at all life stages in this temperate forest, and the strength of this dependence weakens as life stages. The impact of heterospecific negative density dependence (HNDD) on individual survival in different life stages is influenced by the neighborhood scale and exhibits an unclear trend. The survival of individual seedlings is positively influenced by the "herd immunity effect" or a suitable habitat, as neighboring seedlings of the conspecies have a beneficial impact. Interspecific differences in neighborhood effects are influenced by species' life history strategies, life type, and species abundance. The study demonstrates the necessity of incorporating multiple species and life stages when investigating the mechanisms that influence species coexistence in local-scale forest communities.

Key words: Density dependence, Life stages, Neighborhood analysis, Janzen Connell hypothesis