Divergence of environmental filtering: rock exposure rate filters reproductive traits whereas slope shape community richness.

Introduction: Environmental filtering is a core mechanism driving plant functional trait reassembly and community succession. However, it is often treated as a uniform process, and whether distinct abiotic factors act through divergent mechanisms remains poorly understood. Methods: We quantified reproductive traits (fruit types and seed dispersal modes), environmental gradients, and community attributes across plots in a typical resource-limited ecosystem characterized by intensified environmental filtering. Using an integrated framework that combined correlation screening, mediation analysis, and partial correlation confirmation, we identified key environmental factors and disentangled their divergent pathways underlying community richness and reproductive trait composition. Results: Rock exposure was directly associated with reproductive traits, showing consistent negative effects on nut proportion and consistent positive effects on drupe proportion. In contrast, slope was associated with community attributes, corresponding to significantly higher species richness and reproductive trait redundancy but showing no significant association with reproductive trait composition. This pathway divergence corresponds to a decoupling of community richness from reproductive trait composition. Discussion: Our results indicate that different environmental filters influence community richness and the proportion of reproductive traits through divergent pathways in resource-limited ecosystems, resulting in decoupling between community attributes and functional traits. This pathway divergence broadens the understanding of functional trait reassembly along multidimensional gradients, and provides novel insights for vegetation restoration in extreme habitats.