Understanding Effects of Warming on Tundra Soil Organic Carbon Degradation Pathways

Frozen Arctic soils represent one of the largest pools of stored soil organic carbon, but it is unclear which types of SOC are easy to decompose after the soil thaws and what are the degradation mechanisms. Using a suite of chromatographic and spectroscopic techniques, Ziming Yang and co-workers at Oak Ridge National Laboratory examined the dynamic consumption and production of labile SOC in a tundra soil from the Barrow Environmental Observatory, Barrow, Alaska, United States. They found that degradation of simple sugars and alcohol in thawed SOC largely accounts for the initial rapid release of CO₂ and CH₄ by microorganisms in the absence of oxygen. Organic acid fermentation products accumulated over time, fueling later production of CH₄ and CO₂. A conceptual framework for labile SOC transformations and their relations to fermentation, iron reduction, and methanogenesis is proposed for improved model prediction of climate feedbacks in the Arctic.