Mineral-Organic Matter Interactions in Soil Systems

Interactions between soil minerals and organic matter underpin the stability, turnover and sequestration of carbon in terrestrial ecosystems. Mineral surfaces, including clay minerals and iron and aluminium oxides, sorb organic compounds via electrostatic and ligand‐exchange mechanisms, forming organo‐mineral complexes that protect organic carbon from microbial decomposition. Physical occlusion within soil aggregates further shields vulnerable compounds, while redox‐sensitive metal phases can both catalyse the formation of complex macromolecules and, under changing oxygen conditions, release bound carbon. Biotic factors such as microbial adhesion, enzymatic activity and litter chemistry modulate these abiotic controls, creating coupled cycles of mineral transformation and organic matter turnover. Environmental parameters – pH, moisture regime, mineralogy and vegetation type – govern the balance between protection and decomposition. Given the central role of soils in the global carbon cycle, mechanistic understanding of mineral‐organic interactions is essential for predicting responses to land use change, hydrological shifts and climate warming, and for informing soil management practices that enhance carbon retention and fertility.

Research from Nature Portfolio

Recent studies have shown that iron and manganese ions and minerals can abiotically catalyse the Maillard reaction at ambient temperatures relevant to terrestrial margins, transforming simple organic substrates into complex macromolecules and substantially increasing long‐term carbon preservation. Parallel work has revealed that calcium plays a dual role, not only mediating physicochemical binding of plant litter to mineral surfaces but also promoting surface‐colonising microbial communities that enhance incorporation of litter into microbial biomass, thereby increasing carbon use efficiency and mineral‐associated organic matter formation. High‐resolution cryo‐electron microscopy coupled with spectroscopic imaging has visualised soil at the nanometre scale to identify discrete organo–organic and organo–mineral interfaces, demonstrating enrichment of nitrogen and oxidised carbon at these contact zones and highlighting the importance of nitrogen‐rich residues in stabilising carbon pools.

Mineral-Organic Matter Interactions in Soil Systems publication trend

The graph below shows the total number of articles in mineral-organic matter interactions in soil systems across all publications each year (not limited to Nature Index journals).

Technical terms

Organo-mineral complexes: Assemblages where organic molecules are bound to mineral surfaces through sorptive or covalent interactions.

Soil organic carbon (SOC): The carbon component of organic compounds in soil derived from plant, animal and microbial residues.

Density fractionation: A laboratory method to separate soil organic matter into physical fractions used to infer stability and protection mechanisms.

Organo–organic interfaces: Contacts between distinct organic phases in soil aggregates not directly associated with minerals.

Reactive iron oxides: Mineral phases such as ferrihydrite and goethite that strongly sorb organic compounds and influence redox processes.

References

1. Long-term organic carbon preservation enhanced by iron and manganese. Nature (2023).
2. Calcium promotes persistent soil organic matter by altering microbial transformation of plant litter. Nature Communications (2023).
3. Organo–organic and organo–mineral interfaces in soil at the nanometer scale. Nature Communications (2020).
4. Metallic protection of soil carbon: divergent drainage effects in Sphagnum vs. non-Sphagnum wetlands. National Science Review (2024).
5. Storage and stability of organic carbon in soils as related to depth, occlusion within aggregates, and attachment to minerals. Biogeosciences (2013).
6. Iron-bound organic carbon in forest soils: quantification and characterization. Biogeosciences (2016).