Abstract
Hydrological regime is widely recognized as the primary driver shaping riparian vegetation, yet its mechanistic links with taxonomic, functional, and ecosystem diversity under dam-regulated conditions remain insufficiently quantified. In this study, we quantified flow regime characteristics in the Three Gorges Reservoir (TGR). We identified five statistically distinct flow regime types using hierarchical clustering based on magnitude, duration, frequency, average flooding intensity, and rate of change. Significant differences among the five flow regime types were observed using one-way ANOVA with Tukey HSD post hoc tests (p < 0.05), particularly in magnitude, duration, flooding intensity, and rate of change, while flooding frequency showed no significant variation. Species richness was negatively associated with flooding duration but positively associated with hydrological conditions of milder flow regime types, especially during early and late growing seasons (April and September). Functional diversity increased along the flow regime gradient and exhibited a significant positive association with species richness. After statistical re-evaluation, only linear relationships were retained (p < 0.05). The results demonstrate that flow regime is a more reliable predictor of riparian vegetation zonation and functional diversity than flooding duration alone, emphasizing the role of hydrological variability in shaping ecosystem functioning within large regulated reservoirs.