Soil Processes and Climate Solutions: From Carbon Cycling to Climate-Smart Land Management

Soil organic carbon is widely used as the principal indicator of soil carbon sequestration, yet a single bulk stock obscures organic matter pools that differ in formation pathway, persistence, nutrient stoichiometry, management responsiveness and vulnerability to environmental change. This critical narrative review evaluates particulate organic matter and mineral-associated organic matter as complementary targets for climate-smart soil management. Literature published primarily from 2000 to 8 July 2026 was selected from major open scholarly databases and indexes, with older foundational studies retained where necessary. The synthesis shows that particulate organic matter is generally more responsive to recent carbon inputs and disturbance, supports aggregation and nutrient cycling, and can persist when physically protected or environmentally inaccessible. Mineral-associated organic matter is, on average, longer lived because of organo-mineral interactions, but its formation is controlled jointly by substrate supply, microbial transformation, mineral reactivity, stoichiometry and accessibility. Evidence does not support a universal assumption that mineral-associated organic matter is either microbially derived, permanently stable or constrained by a simple clay-based saturation ceiling. Likewise, management effects cannot be reduced to a choice between rapidly accumulating particulate carbon and durable mineral-associated carbon: outcomes depend on initial soil carbon, mineralogy, texture, pH, climate, depth, plant traits, nutrient supply and timescale. Recent warming and drought studies further demonstrate that mineral association attenuates, but does not eliminate, climate vulnerability. A fraction-aware management framework is therefore most defensible when total soil organic carbon remains the accounting baseline, while particulate and mineral-associated fractions diagnose mechanisms, persistence and management leverage. Standardised fractionation, whole-profile stock accounting, age or source validation, and integration with greenhouse-gas and productivity outcomes are priorities for translating fraction science into credible climate-smart practice.