Riparian plant community structure and assembly processes differed by variations in riverbank curvatures: implications for restoring habitats along the Three Gorges Reservoir

Abstract

A meandering riverbank plays a vital role in maintaining natural river ecosystems, providing habitats for riparian vegetation. However, dams have significantly altered riverbank shapes. To restore the riparian ecosystems, it is imperative to understand how different riverbank curvatures influence them. This study aims to uncover the ecological impacts of riverbank curvature on the structure and assembly process of plant communities in the riparian zone of the Yangtze River, regulated by the Three Gorges Dam (TGD) in China. We categorized the riparian zones into four types: cove, lobe, wavy and linear shapes. We documented the composition and diversity of riparian plant communities. Our findings revealed that wavy and cove riverbanks exhibited greater species diversity (with Shannon-Wiener diversity index values 1.5× higher) compared to communities along linear riverbanks. Furthermore, the analysis of functional traits indicated that wavy riverbanks promoted the differentiation of plant functional traits, thus enhancing ecosystem functions, with functional dispersion index (FDis) values 1.3 times higher than those of linear riverbanks. Significant variations in the assembly of riparian communities were also observed among different riverbanks, with standardized effect size (SES) values indicating a higher degree of niche differentiation in cove riverbanks (SES = 0.4) compared to linear riverbanks (SES = -0.6). These results highlight the ecological importance of diverse riverbank curvatures in influencing the diversity, structure and assembly of riparian communities along the waterway. In summary, this study underscores the necessity of maintaining or restoring various natural morphological curvatures when rehabilitating riparian communities along rivers impacted by human activities.