Abstract:

Aims: Submerged macrophytes play a crucial role in maintaining the health and stability of shallow lake ecosystems. Understanding their long-term dynamics and driving factors has significant theoretical and practical implications for the ecological restoration and eutrophication control of lakes.
Method: We analyzed the α- and β-diversity patterns of submerged macrophytes over the nearly 70 years (1954-2021) focused on the 17 lakes in the middle and lower reaches of the Yangtze River. The β-diversity was further decomposed into turnover and nestedness components using the Sørensen dissimilarity index. This method allowed us to explore the linkages between changes in the lake environmental heterogeneity and the submerged macrophyte community diversity patterns.
Results: (1) At the lake scale, α-diversity of submerged macrophytes exhibited a decreasing trend in 11 lakes, while most lakes presented no significant changes in β_temporal-diversity (variations in community structure between different years within the same lake). This result was primarily driven by the nestedness component. (2) At the watershed scale, the α-diversity of submerged macrophytes showed a trend of increasing first and then decreasing during the evolutionary process. The β_spatial-diversity (variations in community structure between different lakes during the evolutionary process) exhibited a gradual decrease, while lake environmental heterogeneity showed a gradual increase. (3) Lakes with higher environmental heterogeneity tended to have lower α-diversity and higher β-diversity. These changes were likely the combined result of various factors including human activities, water pollution, hydrological changes, and climate variability.
Conclusion: Although the specific mechanisms require further investigation, we contribute to current research by providing theoretical significance for the management and conservation of lake ecosystems in the middle and lower Yangtze River Basin. Our study provides a scientific basis for formulating effective conservation strategies and measures.

Key words: submerged macrophyte, lakes, α-diversity, β-diversity, community succession, environmental heterogeneity