Estimating influences of environmental drivers on soil heterotrophic respiration in the Athabasca River Basin, Canada

Soil heterotrophic respiration (R-H) is a crucial component of the atmospheric carbon dioxide (CO2) budget, as R-H accounts for similar to 10 times more CO2 than burning fossil fuels. However, modelling of R-H is primarily based upon empirical/semi-empirical approaches. Here, we developed a mechanistic model based on microbial kinetics and thermodynamics processes (MKT) to model soil chemical environment and soil R-H in the Athabasca River Basin, Canada. MKT was coupled with the Soil and Water Assessment Tool (SWAT) for a regional-scale hydro-biogeochemical simulation. Dissolved oxygen, redox potential and meteorological variables were simulated for the first time at a regional scale. Annual mean simulated RH varied from 20 to 320 kg CO2-C/ha/yr across Athabasca River basin (ARB) in 2000-2013. Our results show that dissolved oxygen, air temperature, and soil temperature have more influence on R-H than redox potential, precipitation, and water-filled pore space (WFPS). A significant (p < 0.01) causal relationship exists between the dissolved oxygen, air temperature, soil temperature, redox potential and precipitation with R-H. Our results show that the role of environmental drivers are essential and should be considered in future estimations of R-H. (C) 2019 Elsevier Ltd. All rights reserved.