DataSheet1_Trait-based community assembly and functional strategies across three subtropical karst forests, Southwestern China.docx

BackgroundVariations in community-level plant functional traits are widely used to elucidate vegetation adaptation strategies across different environmental gradients. Moreover, studying functional variation among different forest types aids in understanding the mechanisms by which environmental factors and functional strategies shift community structure.
MethodsBased on five plant functional traits, including four leaf and one wood trait, for 150 woody species, we analyzed shifts in the community-weighted mean trait values across three forest types in a karst forest landscape: deciduous, mixed, and evergreen forests. We also assessed the relative contributions of stochastic processes, environmental filtering, and niche differentiation to drive community structure using a trait-based null model approach.
ResultsWe found marked changes in functional strategy, from resource acquisition on dry, fertile soil plots in deciduous forests to resource conservation on moist, infertile soil conditions in evergreen forests. The trait-based null model showed strong evidence of environmental filtering and convergent patterns in traits across three forest types, as well as low niche differentiation in most functional traits. Some evidence of overdispersion of LDMC and LT occurred to partially support the recent theory of Scheffer and Van Nes that competition could result in a clumped pattern of species along a niche axis.
DiscussionOur findings suggest a change in environmental gradient from deciduous to evergreen forest, together with a shift from acquisitive to conservative traits. Environmental filtering, stochastic processes, niche differentiation, and overdispersion mechanisms together drive community assembly in karst forest landscapes. These findings will contribute to a deeper understanding of the changes in functional traits among karst plants and their adaptive strategies, with important implications for understanding other community assemblies in subtropical forest systems.

研究背景：群落水平的植物功能性状变异被广泛用于阐明不同环境梯度下的植被适应策略。此外，探究不同森林类型间的功能变异，有助于理解环境因子与功能策略驱动群落结构变化的内在机制。
研究方法：本研究基于150种木本植物的5项功能性状（含4项叶片性状与1项木质部性状），分析了喀斯特森林景观中3类森林（落叶林、混交林与常绿林）的群落加权平均性状值的变化规律。同时，本研究采用基于性状的零模型方法，评估了随机过程、环境过滤与生态位分化在驱动群落结构形成中的相对贡献。
研究结果：本研究发现植物功能策略存在显著变化：落叶林的植物偏向于在干燥肥沃的生境中采取资源获取策略，而常绿林的植物则在湿润贫瘠的土壤条件下采用资源保守策略。基于性状的零模型分析显示，三类森林的功能性状均表现出显著的环境过滤与性状趋同模式，且多数功能性状的生态位分化程度较低。部分结果显示LDMC与LT存在性状过离散现象，这在一定程度上支持了Scheffer与Van Nes提出的最新理论——即种间竞争可导致物种沿生态位轴呈现聚集分布格局。
讨论：本研究结果表明，从落叶林到常绿林的环境梯度变化，伴随植物功能性状从资源获取型向资源保守型的转变。环境过滤、随机过程、生态位分化以及性状过离散机制共同驱动了喀斯特森林景观的群落构建过程。本研究有助于更深入地理解喀斯特植物功能性状的变异规律及其适应策略，对探究亚热带森林生态系统中的其他群落构建过程具有重要借鉴意义。