Enhancing ecological functions of Taxodium hybrid plantations in the Dianchi Lake riparian zone: A case study on nitrogen and phosphorus removal

Riparian plantations of Taxodium hybrid ‘Zhongshanshan’ (hereafter Zhongshanshan) have been widely established along the shoreline of Dianchi Lake (Southwest China) as eco-engineering buffers to intercept non-point source nitrogen (N) and phosphorus (P). However, nutrient retention under contrasting hydrological regimes and its governing controls remain poorly constrained. We compared two representative Zhongshanshan stands: a seasonally flooded site with wet–dry alternation (LWM) and a permanently flooded site under continuous inundation (LYH). Surface (0-15 cm) and subsoil (30-50 cm) soils were sampled along the runoff pathway from the inflow side toward the lake. Both stands showed clear declines in total nitrogen (TN) along the transect, with mean reductions of ~28.9% (LWM) and ~39.4% (LYH), and LYH also exhibited substantial total phosphorus (TP) removal (up to ~36.5%). In contrast, ammonium-N (NH₄⁺-N), nitrate-N (NO₃⁻-N), and available phosphorus (AP) occasionally increased toward the lakeward edge, indicating potential secondary release hotspots. Spearman correlations and redundancy analysis suggested that ferric iron (Fe³⁺) was the strongest correlate of N and P attenuation under seasonal flooding, whereas soil organic matter was the key predictor under permanent inundation. Concurrent shifts in bacterial community structure, including elevated relative abundance of Bacillus asahii , were associated with nutrient accumulation or depletion patterns. Our results highlight the importance of hydrology-adapted buffer design and management; moderate planting density (avoiding overly dense stands), a mixed tree–shrub–herb understorey, and ~3 m × 3 m spacing are recommended to enhance nutrient interception and support eutrophication mitigation in plateau lakes such as Dianchi Lake. Nitrogen and Phosphorus Removal Mechanisms in Taxodium Hybrid Riparian Forests of Dianchi Lake This study investigated two Taxodium hybrid (commonly known as Chinese pond cypress) plantations located in the Dianchi Lake watershed under contrasting hydrological conditions. The research aimed to evaluate the efficiency of these riparian forests in reducing nitrogen and phosphorus along vertical soil profiles and along the direction of non-point source runoff. Soil physicochemical properties were analyzed to identify the environmental factors influencing nutrient removal performance. Furthermore, the relationships between bacterial community composition and nutrient concentrations were examined to determine potential microbial taxa contributing to nitrogen and phosphorus attenuation. The findings provide practical guidance for the ecological management and scientific establishment of Taxodium hybrid plantations in the plateau lake supporting their role in enhancing nutrient removal and improving riparian ecosystem functions. making our work well-suited for publication in the Evironmental Technology & Innovation . • Comparison of seasonal vs. permanent flooding in Taxodium hybrid ‘Zhongshanshan’ stands at Dianchi Lake. • TN reduced by 28.9–39.4%; TP decreased by 25.1% in Laoyuhe woodland. • Fe³⁺ dominates nutrient removal under dry–wet cycles; SOM leads in flooding. • Bacillus asahii dominated and correlated with N and P forms under varying sites. • Tree–shrub–grass design (3×3 m) enhances Taxodium N and P removal efficiency.