VOCs Impact Soil Carbon Transformations and Sequestration

Abstract Soil constitutes the largest terrestrial reservoir of organic carbon, yet small reactive volatile organic compounds (VOCs) from plants and microbes are often overlooked in carbon cycling models. We investigated the impact of five common VOCs (methanol, acetaldehyde, acetone, isoprene, and α‐pinene) on soil carbon dynamics using controlled incubations and advanced metabolomic analyses. VOC‐induced carbon retention ranged from 22% to 72%, with most carbon ending up as total inorganic carbon. Within the organic fraction, VOCs substantially reshaped the soil metabolome: acetaldehyde was efficiently converted to complex carbon forms with potential for long‐term stabilization, methanol and acetone were largely respired by microbes, isoprene persisted under low‐moisture conditions and α‐pinene exhibited bidirectional carbon flow. Depending on their chemical structure and environmental conditions, VOCs were either quickly assimilated or transformed into complex long‐lived metabolites. These results demonstrate that VOCs can contribute substantially to soil carbon storage and highlight the need to include these small molecules in biogeochemical models to improve predictions of carbon dynamics and climate feedback.