Multidimensional Partitioning of β‐Diversity in a Large Temperate‐Boreal Forest Region

ABSTRACT Aim β‐diversity quantifies spatial variation in community composition, indicating species replacement or richness difference between different locations or habitats. Understanding the multidimensional patterns and components of β‐diversity is essential for disentangling community assembly processes and guiding biodiversity conservation. However, traditional β‐diversity studies predominantly focus on species diversity while the functional and phylogenetic dimensions are often neglected or overlooked. Location Northeast China. Taxon Trees. Methods Using a large‐scale forest inventory dataset comprising 412 plots (0.1 ha each) across Northeast China, one of the world's most extensive temperate‐boreal forest regions, we quantified β‐diversity across species, functional, and phylogenetic dimensions within a unified framework. We further decomposed total β‐diversity into replacement and richness difference components and assessed the local contribution to β‐diversity (LCBD) to identify ecologically unique sites. Forward selection and variation partitioning were applied to disentangle the relative roles of environmental and spatial processes in shaping community uniqueness. Results We found that replacement consistently dominated β‐diversity across all dimensions, although its relative contribution declined when functional and phylogenetic information was incorporated, indicating that species turnover often involved functionally or phylogenetically similar taxa. Sites with high LCBD were concentrated in species‐poor regions, particularly in the northwestern boreal forests, where functional and phylogenetic uniqueness was disproportionately high. Both environmental filtering and dispersal limitation jointly shaped community uniqueness, with stronger effects detected in functional and phylogenetic dimensions. Main Conclusions Our findings demonstrate that integrating multiple dimensions of β‐diversity provides a more comprehensive understanding of forest biodiversity patterns and improves the identification of conservation priorities beyond species richness alone. In particular, we highlight that boreal forests with high functional and phylogenetic distinctiveness warrant greater conservation attention, which is especially relevant to the ongoing forest ecological protection and restoration initiatives in Northeast China.