Soil CO2 Emission Largely Dominates the Total Ecosystem CO2 Emission at Canadian Boreal Forest

• Published in: Frontiers in Environmental Science
• Main Authors: Bhanja, Soumendra N., Wang, Junye, Bol, Roland
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Frontiers Media SA 2022
• Subjects: General Environmental Science; Athabasca River; Subarctic
• Online Access: http://dx.doi.org/10.3389/fenvs.2022.898199; https://www.frontiersin.org/articles/10.3389/fenvs.2022.898199/full

The natural carbon dioxide (CO 2 ) emission from the ecosystem, also termed as the ecosystem respiration (R eco ), is the primary natural source of atmospheric CO 2 . The contemporary models rely on empirical functions to represent decomposition of litter with multiple soil carbon pools decaying at different rates in estimating R eco variations and its partitioning into autotrophic (R a ) (originating from plants) and heterotrophic (originating mostly from microorganisms) respiration (R h ) in relation to variation in temperature and soil water content. Microbially-mediated litter decomposition scheme representation are not very popular yet. However, microbial enzymatic processes play integral role in litter as well as soil organic matter (SOM) decomposition. Here we developed a mechanistic model comprising of multiple hydro-biogeochemical modules in the soil and water assessment tool (SWAT) code to explicitly incorporate microbial-enzymatic litter decomposition and decomposition of SOM for separately estimating regional-scale R a , R h and R eco . Modeled annual mean R eco values are found varying from 1,600 to 8,200 kg C ha −1 yr −1 in 2000–2013 within the boreal forest covered sub-basins of the Athabasca River Basin (ARB), Canada. While, for the 2000–2013 period, the annual mean R a , R h and soil CO 2 emission (R s ) are varying within 800–6,000 kg C ha −1 yr −1 , 700–4,200 kg C ha −1 yr −1 and 1,200–5,000 kg C ha −1 yr −1 , respectively. R s generally dominates R eco with nearly 60–90% contribution in most of the sub-basins in ARB. The model estimates corroborate well with the site-scale and satellite-based estimates reported at similar land use and climatic regions. Mechanistic modeling of R eco and its components are critical to understanding future climate change feedbacks and to help reduce uncertainties particularly in the boreal and subarctic regions that has huge soil carbon store.