International Journal of Plant & Soil Science

Soil microorganisms influence terrestrial carbon cycling by regulating the transformation, release and retention of plant-derived organic carbon. This review examines the biological and physicochemical mechanisms through which the soil microbiome contributes to soil organic carbon sequestration and considers their responses to climate change. Bacteria, fungi, archaea and other soil microorganisms decompose organic substrates, assimilate carbon into biomass and generate microbial residues that may become associated with mineral surfaces or protected within soil aggregates. Microbial carbon-use efficiency, extracellular polymeric substances, microbial necromass formation and rhizosphere interactions therefore influence the balance between carbon mineralisation and stabilisation. Temperature, drought, rewetting and altered oxygen availability can affect microbial community composition, enzyme activity and greenhouse gas fluxes, although their consequences for persistent carbon pools depend on soil and environmental conditions. The review also considers the roles of plant root exudates, mycorrhizal associations, nutrient availability and particulate and mineral-associated organic matter in carbon dynamics. Sustainable practices, including reduced tillage, cover cropping, organic amendments, biochar application and microbial inoculants, are discussed as possible approaches to improving carbon retention under suitable conditions. Metagenomics, other multi-omics methods and stable-isotope techniques offer complementary means of investigating microbial functions and carbon transformations. Overall, integrating microbial processes with soil mineralogy, climate responses and context-specific management may improve understanding of soil carbon persistence and inform climate change mitigation strategies.