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Purpose <p>The molecular composition and transformation of dissolved organic matter (DOM) in subtropical acidic red soils critically influence soil carbon-nitrogen cycling, yet remain poorly understood due to complex parent material (PM) environment interactions.</p> Methods <p>This study integrated UV-Vis, three-dimensional fluorescence spectroscopy (3D-EEM), Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), and partial least squares path modeling (PLS-SEM) to investigate three red soil types (Clayey Acrisols (CA), Sandy Acrisols (SA), and Clay Loam Acrisols (CLA)) from distinct PMs in Shanggao, Jiangxi.</p> Results <p>All soils shared a core DOM pool (43% of molecules), dominated by lignins and lipids, reflecting PM’s “initial filtering” role. However, unique molecular libraries diverged along three transformation pathways: mineral<i>-</i>protected, highly aromatic DOM in CA; oxidation<i>-</i>driven, rapidly cycling DOM in SA; and microbe-mineral coupled DOM in CLA, enriched in recalcitrant hydrophobic components yet depleted in microbial markers (amino sugars). Multivariate analyses consistently identified soil pH and active manganese oxides (Mn<sub>d</sub>) as the core drivers of DOM differentiation, especially its nitrogen characteristics. The PLS-SEM model quantified a strong synergistic “pH–Mn<sub>d</sub>” effect on DOM nitrogen characteristics (amino sugars, N/C ratio; path coefficient = 0.877). Mechanistically, pH optimizes microbial activity and nitrogen bioavailability, while Mn<sub>d</sub> acts as an oxidation-adsorption coupler, jointly promoting the synthesis and stabilization of microbially derived nitrogen-rich DOM. This driving pathway shifted optical indices toward higher humification and lower autochthonous contribution, though the anomalous SUVA₂₅₄ response cautions against over relying on single spectral proxies in complex soils.</p> Conclusion <p>This work establishes an integrated model of “parent material preset — core environmental drivers — pathway differentiation,” providing a quantitative basis for enhancing carbon and nitrogen co-sequestration in acidic red soils through precise pH adjustment (4.8—5.2) and manganese management.</p>

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Study on molecular characteristics of dissolved organic matter in red soils under different parent materials

  • 期刊论文

  • 发表日期：

    2026年7月30日

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  • Xiaodi Cheng,
  • Qin Zhang,
  • Yiyue Zhao,
  • Guanjie Jiang,
  • Yupeng Yan,
  • Xiaomin Zhao

摘要

Purpose

The molecular composition and transformation of dissolved organic matter (DOM) in subtropical acidic red soils critically influence soil carbon-nitrogen cycling, yet remain poorly understood due to complex parent material (PM) environment interactions.

Methods

This study integrated UV-Vis, three-dimensional fluorescence spectroscopy (3D-EEM), Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), and partial least squares path modeling (PLS-SEM) to investigate three red soil types (Clayey Acrisols (CA), Sandy Acrisols (SA), and Clay Loam Acrisols (CLA)) from distinct PMs in Shanggao, Jiangxi.

Results

All soils shared a core DOM pool (43% of molecules), dominated by lignins and lipids, reflecting PM’s “initial filtering” role. However, unique molecular libraries diverged along three transformation pathways: mineral-protected, highly aromatic DOM in CA; oxidation-driven, rapidly cycling DOM in SA; and microbe-mineral coupled DOM in CLA, enriched in recalcitrant hydrophobic components yet depleted in microbial markers (amino sugars). Multivariate analyses consistently identified soil pH and active manganese oxides (Mnd) as the core drivers of DOM differentiation, especially its nitrogen characteristics. The PLS-SEM model quantified a strong synergistic “pH–Mnd” effect on DOM nitrogen characteristics (amino sugars, N/C ratio; path coefficient = 0.877). Mechanistically, pH optimizes microbial activity and nitrogen bioavailability, while Mnd acts as an oxidation-adsorption coupler, jointly promoting the synthesis and stabilization of microbially derived nitrogen-rich DOM. This driving pathway shifted optical indices toward higher humification and lower autochthonous contribution, though the anomalous SUVA₂₅₄ response cautions against over relying on single spectral proxies in complex soils.

Conclusion

This work establishes an integrated model of “parent material preset — core environmental drivers — pathway differentiation,” providing a quantitative basis for enhancing carbon and nitrogen co-sequestration in acidic red soils through precise pH adjustment (4.8—5.2) and manganese management.