Seed bank contributions and environmental filtering shape seasonal dynamics and restoration potential of submerged macrophytes in Baiyangdian Lake

Introduction Submerged macrophytes are essential for maintaining the structure and functioning of shallow lake ecosystems. Seasonal environmental fluctuations strongly shape the structure and recovery capacity of submerged macrophyte communities. Methods To evaluate seasonal recovery potential and environmental constraints in Baiyangdian Lake, we integrated species richness, biomass, community structure, β−diversity components, and assembly processes with water and sediment variables based on field surveys, seed bank germination experiments, and multivariate analyses. Results The results showed that seed bank had the highest species richness and contained four unique species, whereas richness in submerged macrophyte communities declined steadily from spring to autumn. PERMANOVA revealed significant seasonal differences in community structure (R² = 0.1662, P = 0.001). β−diversity partitioning indicated that richness differences dominated community assembly in spring and summer, whereas species replacement became predominant in autumn. Deterministic processes dominated community assembly overall, with environmental filtering strongest in autumn. Key environmental drivers shifted seasonally: chlorophyll-a ( Chl.a ), ratio of secchi depth (SD) to water depth (WD), and sediment total phosphorus (STP) were significant in spring; STP was the sole significant driver in summer; and sediment organic matter (SOM) emerged as the primary driver in autumn. Using a decision-matrix framework that integrates recovery potential and environmental pressure, we classified site trajectories into five seasonal types, including continuous high-risk, seasonal improvement, cumulative stress, stable-resistant, and abrupt deterioration, each representing distinct ecological response pathways that highlight differences in resilience, stress accumulation, and management priorities across seasons. Discussion These findings provide a process−based foundation for ecological risk diagnosis and support season−specific restoration and adaptive management in shallow lake ecosystems.