Boreal peatlands contain approximately 500 Pg carbon (C) in the soil, emit globally significant quantities of methane (CH4), and are highly sensitive to climate change. Warming associated with global climate change is likely to increase the rate of the temperature-sensitive processes that decompose stored organic carbon and release carbon dioxide (CO2) and CH4. Variation in the temperature sensitivity of CO2 and CH4 production and increased peat aerobicity due to enhanced growing-season evapotranspiration may alter the nature of peatland trace gas emission. As CH4 is a powerful greenhouse gas with 34 times the warming potential of CO2, it is critical to understand how factors associated with global change will influence surface CO2 and CH4 fluxes. Here, we leverage the Spruce and Peatland Responses Under Changing Environments (SPRUCE) climate change manipulation experiment to understand the impact of a 0–9°C gradient in deep belowground warming (“Deep Peat Heat”, DPH) on peat surface CO2 and CH4 fluxes. We find that DPH treatments increased both CO2 and CH4 emission. Methane production was more sensitive to warming than CO2 production, decreasing the C-CO2:C-CH4 of the respired carbon. Methane production is dominated by hydrogenotrophic methanogenesis but deep peat warming increased the δ13C of CH4 suggesting an increasing contribution of acetoclastic methanogenesis to total CH4 production with warming. Although the total quantity of C emitted from the SPRUCE Bog as CH4 is <2%, CH4 represents >50% of seasonal C emissions in the highest-warming treatments when adjusted for CO2 equivalents on a 100-year timescale. These results suggest that warming in boreal regions may increase CH4 emissions from peatlands and result in a positive feedback to ongoing warming.
Bibliographical noteFunding Information:
We appreciate SPRUCE project support from Paul Hanson and W. Robert Nettles and field assistance from Jordan Archer and Michelle Predi. We thank Tim Moore and two anonymous reviewers for helpful comments on an earlier version of this manuscript. Autochambers were designed in collaboration with Jonathan Perry at Boston University following the models of Jim Tang at the Marine Biological Laboratory and Kathleen Savage at the Woods Hole Research Center. Awards from the US Department of Energy (DOE) Office of Science Graduate Fellowship Program (DE-AC05-06OR23100 to ALG) and DOE SC-0012288 supported this research. All opinions expressed in this paper are the authors’ and do not necessarily reflect the policies and views of DOE.
- climate change
- greenhouse gas flux
- warming experiment