Methane Production Pathway Regulated Proximally by Substrate Availability and Distally by Temperature in a High-Latitude Mire Complex

• Published in: Journal of Geophysical Research: Biogeosciences
• Main Authors: Chang, Kuang‐Yu, Riley, William J., Brodie, Eoin L., McCalley, Carmody K., Crill, Patrick M., Grant, Robert F.
• Language: unknown
• Published: 2022
• Subjects: 54 ENVIRONMENTAL SCIENCES; Stordalen; permafrost; Subarctic
• Online Access: http://www.osti.gov/servlets/purl/1581106; https://www.osti.gov/biblio/1581106; https://doi.org/10.1029/2019jg005355

Projected 21st century changes in high-latitude climate are expected to have significant impacts on permafrost thaw, which could cause substantial increases in emissions to the atmosphere of carbon dioxide (CO 2 ) and methane (CH 4 , which has a global warming potential 28 times larger than CO 2 over a 100-year horizon). However, predicted CH 4 emission rates are very uncertain due to difficulties in modeling complex interactions among hydrological, thermal, biogeochemical, and plant processes. Methanogenic production pathways (i.e., acetoclastic [AM] and hydrogenotrophic [HM]) and the magnitude of CH 4 emissions may both change as permafrost thaws, but a mechanistic analysis of controls on such shifts in CH 4 dynamics is lacking. In this study, we reproduced observed shifts in CH 4 emissions and production pathways with a comprehensive biogeochemical model (ecosys) at the Stordalen Mire in subarctic Sweden. Our results demonstrate that soil temperature changes differently affect AM and HM substrate availability, which regulates magnitudes of AM, HM, and thereby net CH 4 emissions. We predict very large landscape-scale, vertical, and temporal variations in the modeled HM fraction, highlighting that measurement strategies for metrics that compare CH 4 production pathways could benefit from model informed scale of temporal and spatial variance. Finally, our findings suggest that the warming and wetting trends projected in northern peatlands could enhance peatland AM fraction and CH 4 emissions even without further permafrost degradation.