Three-dimensional spatial distribution patterns of riparian vegetation and their structural coordination in the Chishui River, China

Riparian vegetation is vital for river ecosystem sustainability, yet its multi-scale assembly mechanisms remain unclear. This study developed a framework for assessing three-dimensional riparian vegetation structure and used the Lateral–Vertical Coordination (LVC) index as a structural perspective to link longitudinal continuity with lateral flood-pulse dynamics. Results showed that vegetation biomass generally declined downstream with local non-monotonic fluctuations, whereas the Margalef richness index increased, suggesting the combined influence of watershed-scale longitudinal riverine processes and local elevational habitat filtering. Homogeneous Type riparian zones exhibited clear vertical stratification and the highest level of structural coordination (LVC = 0.418), suggesting strong lateral and vertical structural development, whereas Fluctuating Type communities showed the lowest vertical structural evenness, characterized by a canopy–understory discontinuity. Riparian zone width (RZW) emerged as the most important factor driving variation in vegetation composition, contributing 27.09% uniquely and 7.01% jointly with other predictors (total = 34.10% of adjusted R 2 ). Higher LVC suggests that vegetation structures across different dimensions are well-developed and tightly linked, thereby indicating the potential for a more structurally stable vegetation community. This study investigated the combined effects of local hydrological and geomorphic conditions and regional elevational gradients on the formation of three-dimensional riparian vegetation patterns in hilly river systems. The framework offers a robust basis for assessing riparian plant community integrity and for supporting vegetation management and restoration in river systems.