Clay Mineralogy and Soil Biogeochemical Processes

Clay minerals form the reactive matrix of soils, governing water retention, nutrient exchange and contaminant dynamics. The principal clay types—1:1 layer silicates such as kaolinite and halloysite, and 2:1 layer silicates including illite, smectite and vermiculite—differ in layer structure, surface charge and swelling behaviour. These distinctions underpin variations in cation exchange capacity, aggregate stability and the preservation of organic matter. Clay surfaces adsorb nutrients and pollutants, influence soil pH and mediate redox reactions that control the mobility of metals and metalloids. Pedogenic processes drive clay neoformation and transformation: weathering of primary minerals yields secondary clays, while clay minerals themselves can convert from one form to another under changing environmental conditions. Microbial communities colonise clay surfaces, catalysing nutrient cycling and organic matter decomposition. At the landscape scale, clay mineralogy affects soil classification, land use potential and carbon sequestration; at the global scale, it influences biogeochemical cycles of carbon, nitrogen, phosphorus and trace elements, with implications for agricultural productivity, water quality and climate feedbacks.

Research from Nature Portfolio

Recent studies have explored how parent material and microclimate shape clay assemblages in upland soils. In subtropical landscapes, soils derived from granite and limestone host predominantly kaolinite, whereas mixed-layer clays dominate in ancient red clays and 2:1 minerals such as illite and vermiculite predominate in sandstones. Elevation and micro-topographical variation correlate with shifts from 1:1 to 2:1 clay dominance, reflecting gradients in weathering intensity and moisture regime. These patterns serve as indicators of pedogenic stage, redox status and soil taxonomy, improving predictive models of soil development and guiding land-use planning in heterogeneous terrains.

Clay Mineralogy and Soil Biogeochemical Processes publication trend

The graph below shows the total number of articles in clay mineralogy and soil biogeochemical processes across all publications each year (not limited to Nature Index journals).

Technical terms

Kaolinite: A non-expanding 1:1 layer silicate clay mineral with low cation exchange capacity, common in highly weathered soils.

Smectite: A 2:1 expanding clay mineral (including montmorillonite) characterised by high cation exchange capacity and variable interlayer hydration.

Cation Exchange Capacity (CEC): The total capacity of a soil to hold and exchange nutrient cations, reflecting surface charge and clay content.

Pedogenesis: The suite of physical, chemical and biological processes that drive soil formation from parent material over time.

Redox conditions: The oxidation–reduction status of a soil environment, controlling the mobility and speciation of metals and nutrients.

Biogeochemical cycling: The movement and transformation of chemical elements through biological, geological and chemical processes in the Earth system.

References

1. Clay mineral composition of upland soils and its implication for pedogenesis and soil taxonomy in subtropical China. Scientific Reports (2021).
2. The evolution of biogeochemistry: revisited. Biogeochemistry (2020).
3. Ideas and perspectives: Biogeochemistry – some key foci for the future. Biogeosciences (2021).
4. Mobility of iron-oxide associated elements in pseudogley soils; influence of parent material age and land use. Geoderma (2022).