Stabilization in the fate of destabilization: Improving the representation of C stabilization when modeling C decomposition in permafrost-affected soils

Permafrost thaw may stimulate microbial degradation of large soil organic carbon (SOC) stocks, releasing greenhouse gases into the atmosphere. Projecting this feedback to the global carbon (C) balance is urgent, but remains highly uncertain, because complex interactions between soil and microbes make it difficult to capture C dynamics accurately in models. How much CO₂ will be respired is to a high degree dependent on C stabilization and persistence in the soil. SOC may be adsorbed to minerals and thereby unavailable to microbes. Common land surface models ignore this process, potentially overestimating C release from thawing permafrost.

This study investigates the effect of this stabilization mechanism on the decomposition process by applying a process-orientated model approach. We fit a microbial-explicit model, which includes mineral adsorption, to a four-year dataset of aerobic incubations of soils from the Lena River Delta, Siberia. We compare this model to a more conceptual first-order decay model, and to a version without mineral adsorption.

Preliminary results suggest that the mechanistic representation of mineral adsorption is crucial for extrapolations into the future, to avoid depletion of organic C pools or the introduction of artificially long C residence times.  We further emphasize the importance of long-term incubation studies.