Structural characteristics and community formation mechanisms in aquatic plant communities during the near-natural restoration of urban rivers

The ecological restoration of urban rivers is essential for aquatic ecosystem management. Understanding the community formation mechanisms among aquatic plants is key to comprehend the structural and functional recovery of river ecosystems. Urban river restoration lacks systematic research on how near-natural methods shape aquatic plant communities. In this study, we aimed to elucidate the structural changes and key influencing factors of aquatic plant communities in rivers after implementing measures, including lowering water levels, retaining sludge, and supplying reclaimed water in Guangzhou. We also sought to explore the mechanisms underlying plant recovery and community formation. To achieve this, sampling, measurement, and analysis of aquatic plants and hydrological and water quality parameters were conducted in the Chebei, Liede, and Shahe Rivers from autumn 2020 to autumn 2023. The results showed that 126 aquatic plant species were recorded in the three rivers, belonging to 40 families and 86 genera, with Poaceae and Cyperaceae as the predominant families, and a consistent increase in coverage was observed over the four years. Partial correlation analysis revealed that depth was significantly negatively correlated with plant richness, coverage, and diversity. Plant community formation in the three rivers resulted from the combined effects of environmental heterogeneity, dispersal limitations, and species interactions. The randomness characteristics of plant communities gradually weaken as river habitat pressure increases, whereas deterministic characteristics gradually strengthen. The findings provide detailed data and a theoretical basis for understanding the response mechanisms of aquatic plant community restoration in urban rivers. They confirm that near-natural restoration measures can effectively improve the recovery potential of aquatic plants in rivers.