Microbial stability of mineral-associated root exudates governed by mineral association capacity, exudate nitrogen availability and their pH
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View abstract on PubMed
Summary
This summary is machine-generated.Mineral-associated organic carbon (MAOC) stability depends on clay mineral properties and root exudate interactions. Understanding these factors is key to predicting soil carbon persistence and microbial availability.
Area Of Science
- Soil Science
- Biogeochemistry
- Clay Mineralogy
Background
- Low-molecular-weight organic compounds from root exudates bind to clay minerals, reducing microbial availability.
- The microbial stability of mineral-associated organic carbon (MAOC) is influenced by mineral and organic compound properties and their interactions, but this remains poorly understood.
Purpose Of The Study
- To quantify the maximal association capacity of four clay minerals (kaolinite, illite, vermiculite, montmorillonite) and five root exudate compounds.
- To assess the microbial stability of MAOC formed through these interactions.
- To elucidate the factors governing MAOC microbial stability.
Main Methods
- Sorption experiments to determine maximal MAOC content for different mineral-organic compound pairs.
- Model soil incubation for 120 days to assess microbial mineralization of MAOC.
- Analysis of correlations between mineral association capacity, compound properties (size, functional groups), mineral properties (CEC, structure), pH, and mineralization rates.
Main Results
- Maximal MAOC content varied significantly (3.42–93.27 mg C g⁻¹ clay), with mineralization rates ranging from 0.69% to 33.98%.
- Mineral association capacity generally increased with substrate molecular size for kaolinite and illite.
- Specific interactions were observed: montmorillonite with glucose, alanine, N-acetylglucosamine (physical entrapment, H-bonding); vermiculite with oxalic/citric acids (cation bridging); kaolinite with glucose (pore entrapment, H-bonding); illite with organic matter (van der Waals, electrostatic forces).
- Negative correlations between mineral association capacity and mineralization were found, except for oxalic acid at low pH.
- Oxalic acid showed higher association with vermiculite/montmorillonite but lower stability than with illite.
- Early MAOC mineralization was faster for N-containing compounds (alanine > N-acetylglucosamine) due to lower C:N ratios.
Conclusions
- Microbial stability of mineral-associated root exudates is governed by mineral association capacity, exudate nitrogen availability, and pH.
- Clay mineral type, organic compound structure, and their specific interactions significantly control the fate of soil organic carbon.
- These findings highlight the complex interplay between mineralogy and organic matter in determining soil carbon sequestration potential.
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