Large carbon losses from burned permafrost peatlands during post-fire succession

The carbon (C) storage of boreal peatlands is threatened by an intensifying wildfire regime. Between 2019 and 2023 we used eddy covariance and surface closed chambers to monitor two permafrost peatlands in boreal western Canada that burned in 2019 and 2007. Deeper thaw, warmer soils, and slow vegetation recovery caused the 2019 Burn to be a net carbon dioxide (CO2) source (+104 g C m-2 yr-1) for four years post-fire, despite reduced soil respiration. The 2007 site was a sink (-35 g C m-2 yr-1) 12 to 15 years post-fire, similar to undisturbed peatlands. We estimate that wildfire caused a loss (~2,500 g C m-2) from permafrost peatlands, with ~1,700 g C m-2 due to combustion and ~800 g C m-2 due to net CO2 losses during post-fire succession. This highlights the importance of the post-fire CO2 losses and emphasizes the vulnerability of permafrost peatland soil C to fire.