Abstract:

Aims: β diversity is a key facet of biodiversity, reflecting variation in species composition across space and time. Exploring the distribution patterns and ecological processes underlying β diversity helps clarify the mechanisms that maintain biodiversity, thereby informing conservation strategies. While β diversity can be partitioned into distinct components, the relative contributions of these components remain poorly understood in temperate coniferous-broadleaf mixed forests. 

Methods: This study used vegetation survey data from a 30-ha forest dynamics plot in coniferous-broadleaf mixed forests in Jiaohe, Jilin Province. The Podani decomposition method was applied to partition the Jaccard and Sørensen dissimilarity indices into species replacement and richness difference components. Additionally, the total variance of the site-by-species abundance matrix was used to quantify β diversity, which was further decomposed into species contribution to β diversity (SCBD) and local contribution to β diversity (LCBD). Relationships between SCBD and species frequency, and between LCBD and species richness, were examined using linear and quadratic regression analyses. Finally, variation partitioning was conducted to assess the relative roles of environmental filtering and dispersal limitation in shaping ecological uniqueness within the forest communities. 

Results: (1) Forest β diversity was predominantly driven by species replacement, while species richness difference contributed less. (2) SCBD showed a significant inverted U-shaped relationship with species frequency, with Carpinus cordata contributing the most and Crataegus maximowiczii the least to β diversity. (3) LCBD exhibited a significant U-shaped relationship with species richness. (4) Both environmental filtering and dispersal limitation influenced forest ecological uniqueness, with dispersal limitation exerting a stronger effect. 

Conclusion: This study reveals the spatial distribution patterns and ecological drivers of β diversity and its components in temperate coniferous-broadleaf mixed forests. The findings deepen understanding of β diversity formation mechanisms in temperate forests and provide a scientific basis for ecological restoration and biodiversity conservation of secondary forests in Northeast China.

Key words: β diversity, species replacement, richness difference, environmental filtering, dispersal limitation