Functional diversity of woody plant communities and its driving factors in the northern Hainan volcanic lava region

Objective To assess woody plant community functional diversity and its main environmental drivers in the northern Hainan volcanic lava region, a tropical volcanic landscape with marked habitat heterogeneity. Methods Woody plant communities were surveyed in the field, leaf functional traits were measured, and nonparametric tests, correlation analysis, redundancy analysis (RDA), and structural equation modeling (SEM) were used to evaluate functional-diversity patterns and potential direct and indirect driver pathways. Results Community-weighted mean values of leaf area (LA), leaf dry matter content (LDMC), chlorophyll a/b ratio (Chl a/Chl b), leaf dry weight (LDW), and leaf tissue density (LTD) were higher in trees than in shrubs ( p < 0.001). Functional richness (FRic), functional dispersion (FDis), and Rao’s quadratic entropy (RaoQ) were also higher in trees ( p < 0.001). Mean annual precipitation (MAP), soil pH, and aggregation index (AI) were the main drivers for the whole community, tree layer, and shrub layer, respectively. SEM suggested that meteorological and environmental factors, anthropogenic-disturbance, and landscape factors may affect functional diversity both directly and indirectly through soil properties. Conclusion Functional diversity in this volcanic lava ecosystem is shaped by multiple environmental pathways, with soil properties playing an important mediating role. These findings provide evidence for conserving and managing woody plant communities in tropical volcanic landscapes.