Abstract: Elucidating the differential responses of riparian plant dispersal traits to hydrological heterogeneity and their associations with species and phylogenetic diversity is critical for ecological restoration in riparian zones. We categorized four types of hydrological heterogeneity zones from small to large in the Three Gorges Reservoir based on the scale of hydrological variation: low elevation area and high elevation area, confluence area and non-confluence area, southern riverbank area, and northern riverbank area, fluctuating backwater area and stable backwater area. Within these four hydrological heterogeneity zones, we compared the differential responses of plant communities in terms of dispersal traits, species diversity, and phylogenetic diversity at both alpha and beta scales. The results showed that plant communities in the fluctuating and stable backwater areas exhibited significant differences in dispersal traits at both alpha and beta scales compared to other hydrological heterogeneity zones. Specifically, in the fluctuating backwater area, dispersal trait diversity showed a significant positive correlation with species richness and phylogenetic diversity, whereas no correlations were observed in the stable backwater area. These findings demonstrate that large-scale hydrological heterogeneity along the flow direction, induced by dam construction, is a dominant factor governing plant dispersal and community assembly in riparian zones. Furthermore, the results suggest that discontinuities in hydrological regimes along the flow direction may create dispersal limitations. Consequently, ecological restoration efforts in the riparian zones should prioritize enhancing hydrological and ecological connectivity between fluctuating and stable backwater areas.

Key words: Three Gorges Reservoir, hydrological heterogeneity, riparian zone, plant community, biodiversity