How Do the Functional Resemblance Structure and Its Component-Dependence Change Among the Successional Stages in Degraded Karst Forests?

The functional resemblance structure, which mainly involved the taxonomic and functional β-diversity, plays a key role in understanding the assembly process during succession in heterogeneous ecosystems. Systematically comparing the functional resemblance structure is essential for uncovering the successional mechanisms since taxonomic and functional β-diversity co-vary. In this study, a series of plots were established among the successional stages in a heterogeneous karst forest. The functional resemblance structure was quantified based on the measured plant functional traits to synchronously compare the changes in taxonomic and functional β-diversity among the successional stages. The results showed that the taxonomic and functional β-diversity varied asynchronously across the successional stages, reflecting the changes in functional beta redundancy. In addition, the functional local contribution to β-diversity was higher in the early successional stage. The functional resemblance structure was dominated by functional beta redundancy, with functioning resilience showing an increasing trend during succession, even in the extremely sensitive karst forests. Furthermore, soil properties mainly determined taxonomic β-diversity while topography primarily affected the functional dimension. Our findings highlighted the importance of functional beta redundancy in determining the functional resemblance structure and emphasized the necessity of synchronous comparison components of the functional resemblance structure when performing the β-diversity analyses.