Potential of soil minerals to sequester soil organic carbon

Summary

This study examined how specific soil minerals influence the capacity of tropical soils to sequester organic carbon, a critical mechanism for atmospheric CO₂ reduction. Using spectroscopic analysis and spatial regression modelling in São Paulo State, Brazil, the authors identified that goethite and gibbsite were primary drivers of carbon sequestration potential in surface soils, whilst hematite and kaolinite dominated at depth, with land use type (particularly pasture-cropping and grassland-forest mosaics) substantially affecting sequestration potential. The findings suggest that soil mineralogy—modifiable through land management—is a key determinant of soil carbon stabilisation capacity.

UK applicability

The mineral-carbon sequestration relationships identified may have limited direct applicability to UK soils, which typically have different clay mineral assemblages (dominated by illite and smectite rather than the iron and aluminium oxides prominent in tropical systems). However, the methodological approach of mapping mineral-specific contributions to carbon sequestration could be adapted for UK soil conditions to inform evidence-based land management for climate mitigation.

Key measures

Soil organic carbon saturation deficit; relative abundance of clay minerals (kaolinite, hematite, goethite, gibbsite) determined by vis-NIR-SWIR spectroscopy; SOC sequestration potential modelled at 0–20 cm and 80–100 cm depths; spatial distribution of mineral contributions to carbon sequestration

Outcomes reported

The study quantified the soil organic carbon (SOC) sequestration potential of clay fractions in tropical soils and identified which clay minerals (kaolinite, hematite, goethite, gibbsite) most strongly explained this potential at different soil depths. The influence of land use type on mineral-mediated carbon sequestration was also assessed using spatial regression modelling and spectroscopic analysis.

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