Soil holds more carbon than the atmosphere and vegetation combined, making it a central part of the global carbon cycle and climate system. Research shows that soil organic carbon is created when plants capture atmospheric carbon dioxide through photosynthesis and transfer it belowground via roots, litter and exudates. Microorganisms then transform this material into more stable organic compounds and mineral‑associated carbon.

Recent work highlights that root inputs are especially important for long‑term carbon storage, often more so than leaves or stems. Fine roots and their exudates feed microbial communities in the rhizosphere, driving the formation of stable soil aggregates and organo‑mineral associations. Fungi and bacteria both contribute, but their roles can differ with depth, vegetation type and soil texture.

Management practices strongly influence soil carbon dynamics. Conservation agriculture, cover crops, reduced tillage and diverse crop rotations tend to increase soil organic carbon by promoting continuous inputs and limiting disturbance. In contrast, intensive tillage, bare fallows and excessive nitrogen fertilization can accelerate decomposition and carbon loss. Grasslands and well‑managed pastures are emerging as significant carbon sinks when grazing intensity is controlled.

Climate change feeds back on soil carbon through warming, altered moisture and extreme events. Higher temperatures generally speed up microbial respiration, potentially releasing stored carbon, especially in high‑latitude and peat soils. However, increased plant growth and deeper rooting in some regions may offset part of these losses.

Overall, soil carbon storage depends on a balance between plant inputs, microbial processing, and physical and chemical protection. Understanding and managing these processes is crucial for climate mitigation, soil fertility and ecosystem resilience.