Modelling soil respiration and its influencing factors for an ongoing peat extraction site

By removing vegetation, installing drainage ditches and harvesting peat, peat extraction changes the hydrological and thermal regimes of the peatlands, which makes the peatlands a strong source of CO2 emissions. We adopted the CoupModel (www.coupmodel.com) to simulate the soil CO2 emissions and its associated abiotic drivers for an ongoing extraction site, located in Riviere-du-Loup (RdL), Quebec Canada. The model was first evaluated against a three year (2019-2021) manual chamber measurements of CO2 flux, soil moisture and temperature profile, and water table depth data. The validated model was then used to assess the impact of changing management practices on the CO2 emission. The simulated CO2 emission was c.a. 200 g C m-2 yr-1, similar to the measured data. The model was also able to reproduce the measured soil moisture, c.a. 10% for the surface harrowed layer (top 3-5 cm depth), which was much lower than the soil layers below, ranging 45-85%, and showed high agreement with the measured temperature and water table depth data. Model sensitivity analysis show the potentially important role of harrowing in regulating the soil respiration. Our modelling suggests the harrowing depth and frequency have large influence on peat evaporation, changing soil moisture and temperature, and ultimately impact the soil CO2 emissions. The spacing of the drainage ditches also influenced the CO2 flux. This study offers insights of implications of management practices on reducing CO2 emissions for peat extraction industry.