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

Abstract

Soil heterotrophic respiration (RH) is a crucial component of the atmospheric carbon dioxide (CO2) budget, as RH accounts for ∼10 times more CO2 than burning fossil fuels. However, modelling of RH 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 RH 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 RH 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 RH. Our results show that the role of environmental drivers are essential and should be considered in future estimations of RH.