Abstract
Peatland carbon cycling is critical for the land–atmosphere exchange of greenhouse gases, particularly under changing environments. Warming and elevated atmospheric carbon dioxide (eCO
2) concentrations directly enhance peatland methane (CH
4) emission, and indirectly affect CH
4 processes by altering hydrological conditions. An ecosystem model ELM-SPRUCE, the land model of the E3SM model, was used to understand the hydrological feedback mechanisms on CH
4 emission in a temperate peatland under a warming gradient and eCO
2 treatments. We found that the water table level was a critical regulator of hydrological feedbacks that affect peatland CH4 dynamics; the simulated water table levels dropped as warming intensified but slightly increased under eCO
2. Evaporation and vegetation transpiration determined the water table level in peatland ecosystems. Although warming significantly stimulated CH4 emission, the hydrological feedbacks leading to a reduced water table mitigated the stimulating effects of warming on CH
4 emission. The hydrological feedback for eCO
2 effects was weak. The comparison between modeled results with data from a field experiment and a global synthesis of observations supports the model simulation of hydrological feedbacks in projecting CH
4 flux under warming and eCO
2. The ELM-SPRUCE model showed relatively small parameter-induced uncertainties on hydrological variables and their impacts on CH
4 fluxes. A sensitivity analysis confirmed a strong hydrological feedback in the first three years and the feedback diminished after four years of warming. Hydrology-moderated warming impacts on CH
4 cycling suggest that the indirect effect of warming on hydrological feedbacks is fundamental for accurately projecting peatland CH
4 flux under climate warming.
Keywords
Warming,
Elevated carbon dioxide,
Hydrology,
Methane,
Model,
Peatland
Citation
Yuan, Fenghui; Wang, Yihui; Ricciuto, Daniel M.; Shi, Xiaoying; Yuan, Fengming; Brehme, Thomas; Bridgham, Scott; Keller, Jason; Warren, Jeffrey M.; Griffiths, Natalie A.; Sebestyen, Stephen D.; Hanson, Paul J.; Thornton, Peter E.; Xu, Xiaofeng. 2021. Hydrological feedbacks on peatland CH4 emission under warming and elevated CO2: A modeling study. Journal of Hydrology. 603: 127137. 12 p. https://doi.org/10.1016/j.jhydrol.2021.127137.