Constructing a Depth-Stratified Model for Soil Organic Carbon: Dynamics of Past, Current, and Future Accumulation and Decomposition

Accumulation and decomposition of soil organic carbon (SOC) have significant impacts on global carbon cycling. Especially, high-latitudinal regions, where a particularly strong warming is expected, currently store large amounts of SOC, and vulnerability against environmental changes are hotly discussed. Due to the expected warming, the SOC in high-latitudinal regions can start to decompose quickly and the resultant carbon dioxide emissions to the atmosphere would further intensify the ongoing climate change. To quantitatively study this land-atmosphere feedback, I developed a depth-stratified SOC model and applied it to a boreal forest site in Alaska. Based on model structure of ED2.0-peat and VISIT, the newly constructed model was designed to reproduce short- (months to several years) and long-term (centuries to millennia) SOC dynamics (Figure a). Since decomposition rates of SOC are highly sensitive to soil environmental conditions (i.e., temperature and moisture), a physics-based approach to simulate belowground thermal and hydrological conditions is used. Moreover, the model simulates radiocarbon dynamics simultaneously with SOC. Current anthropogenic impacts in radiocarbon concentrations such as the Suess effect (since the industrial revolution) and explosions of thermonuclear weapons (mid-20th century) are tracked (Figure b). Since Δ14C was highly sensitive to the recent anthropogenic impacts, a direct comparison against field sampling data will enhance the predictive ability of the model by estimating the recent SOC dynamics. (a) accumulation of soil organic carbon in 2 layers: litter and humus. (b) changes in Δ14C in 2 layers: litter and humus.