Environmental flow increases the riparian vegetation diversity and community similarity

Environmental flow is increasingly used in restoring degraded riparian vegetation. To assess the impact of environmental flow on plant community characteristics and to provide a scientific basis for the subsequent restoration and management of the riparian vegetation at Yongding River (Beijing Section), field surveys were conducted before and after environmental flow application in 2022. Before environmental flow application, sixty-nine species were identified, and the number of species increased to ninety-six species after environmental flow application. Community similarity analysis found that riparian vegetation communities were dominated by emergent hygrophytic plants and the introduced Xanthium italicum had the largest contribution before environmental flow application. The environmental flow increased the proportion of submerged plants, four submerged plant species were among the top ten species contributing to dissimilarity. Canonical correspondence analysis found that soil total nitrogen and organic matter significantly influenced riparian plant richness. Non-metric multidimensional scaling analysis showed that after environmental flow application, the similarity of plant communities in the mountain and plain sections increased. However, it is worth noting that the invasive species Bidens frondosa became dominant in the mountain section, whereas the invasive species Xanthium italicum was widely distributed in the plain section after environmental flow application. The results showed that environmental flow increased mountain section’s vegetation uniformity and plant species richness in the plain section, enhancing plant communities similarity in both regions. Environmental water application supports the spread of both native and invasive species; thus, future management should prioritize the timing of environmental flow to prevent invasive species’ widespread dissemination.