Modeling anaerobic soil organic carbon decomposition in Arctic polygon tundra: insights into soil geochemical influences on carbon mineralization

• Published in: Biogeosciences
• Main Authors: Zheng, Jianqiu, Thornton, Peter E., Painter, Scott L., Gu, Baohua, Wullschleger, Stan D., Graham, David E.
• Language: unknown
• Published: 2023
• Subjects: 54 ENVIRONMENTAL SCIENCES; Arctic; Global warming; permafrost; Tundra
• Online Access: http://www.osti.gov/servlets/purl/1494015; https://www.osti.gov/biblio/1494015; https://doi.org/10.5194/bg-16-663-2019

Rapid warming of Arctic ecosystems exposes soil organic matter(SOM) to accelerated microbial decomposition, potentially leading toincreased emissions of carbon dioxide ( CO 2 ) and methane( CH 4 ) that have a positive feedback on global warming. Currentestimates of the magnitude and form of carbon emissions from Earth systemmodels include significant uncertainties, partially due to the oversimplifiedrepresentation of geochemical constraints on microbial decomposition. Here, wecoupled modeling principles developed in different disciplines, including athermodynamically based microbial growth model for methanogenesis and ironreduction, a pool-based model to represent upstream carbon transformations,and a humic ion-binding model for dynamic pH simulation to build a moreversatile carbon decomposition model framework that can be applied to soilsunder varying redox conditions. This new model framework was parameterizedand validated using synthesized anaerobic incubation data from permafrost-affectedsoils along a gradient of fine-scale thermal and hydrologicalvariabilities across Arctic polygonal tundra. The model accurately simulatedanaerobic CO 2 production and its temperature sensitivity using dataon labile carbon pools and fermentation rates as model constraints. CH 4 production is strongly influenced by water content, pH,methanogen biomass, and presence of competing electron acceptors, resultingin high variability in its temperature sensitivity. This work provides newinsights into the interactions of SOM pools, temperature increase, soilgeochemical feedbacks, and resulting CO 2 and CH 4 production. As a result, the proposed anaerobic carbon decomposition framework presentedhere builds a mechanistic link between soil geochemistry and carbonmineralization, making it applicable over a wide range of soils underdifferent environmental settings.