Soil organic matter (SOM) dynamics play a major role in determining nutrient supply and carbon (C) storage in ecosystems and in regulating atmospheric CO2 concentrations. Better constraints on SOM pools and fluxes are required to advance understanding and generate insight into how global change will influence soil C persistence and vulnerability. This session focuses on empirical, synthesis, and modeling studies addressing the stabilization and change of SOM including but not limited to: storage capacity, ages, and transit times of C in soils, mechanisms of stabilization/destabilization (including new methods for measuring and monitoring change), and ecosystem vulnerability. Studies that feature manipulation experiments (e.g., warming, precipitation, litter), geographically-distributed sites such as meta-analyses or gradients, and model-data integration are strongly encouraged.