Photochemical Emission from Soil as a Source of Atmospheric CO₂

Efflux of carbon dioxide from soil is a central component of the carbon cycle and climate models, but one potentially large source is rarely indicated, namely, photochemical decomposition of soil organic matter. A survey from diverse environments around the world shows that this process is almost ubiquitous and comparable in magnitude to respiration. Moreover, it can persist when respiration subsides, such as in dry and cold soils.