Dispersal, Climate Anomaly and Contemporary Climate Shape the Latitudinal Patterns of β‐Diversity of Angiosperm Trees

Aim The underlying drivers of latitudinal gradients in multifaceted β‐diversity remain debated. The primary focus on abiotic drivers of β‐diversity has left dispersal processes insufficiently explored. This study presents a multiscale analysis of how dispersal, Quaternary climate and contemporary environmental conditions influence multifaceted β‐diversity and its decomposition components in a large temperate forest. Location Northeast China. Time Period 2017. Major Taxa Studied Angiosperm trees. Methods We constructed metacommunities by aggregating multiple sets of local plots to assess taxonomic, functional and phylogenetic β‐diversity across spatial scales. β‐diversity was then partitioned into species replacement and richness difference. Using a community dispersal capacity metric (DCMc), we first evaluated its abiotic drivers and then applied variance partitioning to disentangle the relative contributions of dispersal and environmental filtering to latitudinal patterns of β‐diversity. Spatial simultaneous autoregressive models and structural equation models were then employed to estimate the direct and indirect effects of DCMc and abiotic factors on β‐diversity and its components. Results Environmental filtering emerged as the dominant mechanism of community assembly across scales, whereas dispersal gained importance at broader scales, primarily through spatial and historical structures. We found that DCMc itself represents a legacy of Quaternary climate change. After accounting for abiotic factors, high DCMc values increased richness differences but reduced replacement, while contemporary climate continued to dominate across scales. Interestingly, DCMc had no significant effect on total β‐diversity, whereas temperature anomaly indirectly shaped β‐diversity by influencing DCMc. Main Conclusions Dispersal plays a secondary but significant role relative to environmental filtering in shaping the three facets of β‐diversity, particularly through its mediation of Quaternary climate legacies. Our findings highlight the importance of contemporary climate and reveal distinct pathways by which historical climate shapes different facets of β‐diversity, underscoring the complex interplay between dispersal and environmental filtering in community assembly across scales.