Modelling microbial kinetics and thermodynamic processes for quantifying soil CO₂ emission

Soil respiration is a crucial source of carbon dioxide (CO₂) in the atmosphere. The underlying processes involved are multifaceted, sequential chemical reactions associated with the conversion of soil organic carbon to CO₂. In this paper, we present a mechanistic, biogeochemical model to simulate soil CO₂ emissions considering the microbial and sequential chemical processes using the well-established hydrological model, Soil and Water Assessment Tool (SWAT) for the first time. The soil CO₂ emissions from multiple sequential soil chemical reactions were compared with the observed data at three sites in Canada. The results show that the modelled CO₂ emission rates are in good agreement with the observed data with performance statistics: PBIAS: 0.13%–23%; NSE: 0.27 to 0.62; RSR: 0.60 to 0.84; R²: 0.29 to 0.83. This approach could be used in future regional to global-scale models for simulating the soil CO₂ emission and hydrological processes.