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

Abstract

Soil heterotrophic respiration (R_H) is a crucial component of the atmospheric carbon dioxide (CO₂) budget, as R_H accounts for ∼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 R_H 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.

Keywords: Dissolved oxygen modelling; Redox potential simulation; SWAT; Soil heterotrophic respiration; Soil respiration.