Estimating ecosystem respiration and its components through a new modeling approach in the Soil and Water Assessment Tool (SWAT)

Ecosystem respiration (Reco) is one of the most important processes that controls the atmospheric carbon dioxide (CO2) budget. Estimating the feedback of anthropogenic perturbations on natural Reco emission is crucial keeping in mind the ever-increasing CO2 emissions from various human activities. Importantly, the feedback characteristics of Reco and its components such as the soil respiration (Rs), autotrophic respiration (Ra) and heterotrophic respiration (Rh) are not always equivalent. Here, a new capability has been added to the Soil and Water Assessment Tool (SWAT) model to separately simulate the Rs, Ra, Rh and Reco for the first time. Detailed microbially-mediated carbon cycle processes have been coupled to our mechanistic biogeochemical processes module to simulate the respiration components. The exercises are performed in the cold climate region, Athabasca River Basin (ARB), Canada; mid-latitude boreal forests are the dominant land cover here. Mean annual Reco extends from 1600 to 8200 kg C ha-1 yr-1 between 2000 and 2013 in subbasins of ARB. The modelled estimates are in good agreement with the available site-scale measurements in other Canadian boreal forest locations. It is also found that the ambient temperature (air and soil) and the dissolved oxygen levels in the soil layers are the controlling factors of Reco and its components at ARB.