Synchronous and Asynchronous Variation of Taxonomic and Phylogenetic Diversity During the Succession of <i>Pinus kesiya</i> var. <i>langbianensis</i> Forest in Yunnan, China

The changing patterns of taxonomic diversity (TD) and phylogenetic diversity (PD) during forest succession can provide a reference for optimizing forest ecosystem management. The widely distributed <i>Pinus kesiya</i> var. <i>langbianensis</i> forest (PKF) in subtropical Yunnan, China, has important ecological and economic values. However, little is known about species diversity patterns and driving factors during the pine forest succession. Adopting the "space-for-time-substitution" (SFTS) approach and on the basis of community data from different successional stages, we investigated the dynamics of TD and PD across PKF succession by integrating environmental and spatial variables. The results show that both TD and PD follow a cosine pattern during succession, peaking at mid- to late-successional stages, but with TD lagging behind PD. TD responds more rapidly to changes in dominant environmental factors than PD. Moreover, there is an asynchronous oscillation between taxonomic β diversity (TβD) and phylogenetic β diversity (PβD). TβD is consistently greater than PβD and increases monotonically throughout succession, whereas the PβD still fluctuates in a cosine pattern. TD and PD are equally important in maintaining community stability, and the community becomes increasingly homogeneous and stable. Notably, early and late successional stages are dominated by competitive exclusion, whereas environmental filtering prevailed at mid-succession. The mean temperature of the driest quarter (bio9) plays an environmental filtering role in the community composition at the ecological scale, and the precipitation of the coldest quarter (bio19) shapes the phylogenetic structure by influencing the regional species pool at the evolutionary scale. Neutral and deterministic processes jointly govern β diversity, but niche differentiation has an increasing domination, which supports the "successional continuum hypothesis". Spatial effects must be explicitly considered in SFTS-based successional studies. The management should prioritize conserving mid-successional stages (peak diversity) and balancing environmental heterogeneity with dispersal limitation. Ecological-evolutionary assembly linkages should be considered in the pinewood sustainable utilization and management.