Abstract:

Objective: This paper explores the pattern of species diversity and its scale effects in the Changbai Mountain broad-leaved Korean pine forest based on the individual species-area relationship (ISAR) model. The objective is to gain a deeper understanding of the community structure and the mechanisms maintaining species diversity in broad-leaved Korean pine forests, and to provide a scientific basis for biodiversity conservation and forest management. Method: This study utilized vegetation survey data from a 40-hectare fixed monitoring plot of a broad-leaved Korean pine forest and employed the ISAR model to analyze the impact of target tree species on neighborhood species richness at scales of 0?50 m. The significance of these effects was tested using homogeneous and heterogeneous Poisson?s null models. Furthermore, all tree individuals were categorized by diameter at breast height (DBH) into small-diameter class (5 cm≤DBH<20 cm), medium-diameter class (20cm≤ DBH<40 cm), and large-diameter class (DBH≥40 cm). The impact of individuals of different diameter classes on neighborhood species richness was analyzed in detail, with significance tested using the heterogeneous Poisson?s null model. Result: 1) The species diversity in the neighborhoods of dominant tree species is relatively low. 2) Habitat filtering is not significant at the scale of 0?10 m but significantly affects community species diversity structure at the scale of 11?50 m. 3) Within the scale range of 0?30 m, different tree species exhibit different patterns at varying research scales. At the scale of 31?50 m, most tree species predominantly act as diversity neutral species. 4) Individuals of large, medium, and small diameter classes promote neighborhood species diversity at the scale of 0?10 m, with the small-diameter class having an effect extending up to 14 m. At the scale of 21?50 m, small and medium-diameter individuals mainly exhibit facilitative effects, while large-diameter individuals predominantly show neutral effects. 5) The diversity structure of species within different diameter classes differs at the scale of 0?20 m, influenced by diameter class. However, at the scale of 21?50 m, no differences are observed, with neutral species dominating across all diameter classes. 6) At the scale of 0?10 m, the asymmetric competitive effect of larger-diameter individuals on species within smaller-diameter in the neighborhood is not significant. Asymmetric competition becomes evident at the scale of 14?20 m, with the effect becoming more pronounced as the diameter difference increases. Conclusion: The species diversity pattern of the Changbai Mountain broad-leaved Korean pine forest community is jointly influenced by habitat filtering, tree species characteristics, diameter structure, and interspecific competition, exhibiting significant scale effects. In forest management, it is important to consider ecological processes at different scales, rationally configure tree species and diameter structures, promote species niche differentiation, and reduce asymmetric competition in order to enhance forest biodiversity and resource utilization efficiency.

Key words: individual species-area relationship, habitat filtering, diameter class effect, species diversity