Suppressing peatland methane production by electron snorkeling through pyrogenic carbon in controlled laboratory incubations

Northern peatlands are experiencing more frequent and severe fire events as a result of changing climate conditions. Recent studies show that such a fire-regime change imposes a direct climate-warming impact by emitting large amounts of carbon into the atmosphere. However, the fires also convert parts of the burnt biomass into pyrogenic carbon. Here, we show a potential climate-cooling impact induced by fire-derived pyrogenic carbon in laboratory incubations. We found that the accumulation of pyrogenic carbon reduced post-fire methane production from warm (32 degrees C) incubated peatland soils by 13-24%. The redox-cycling, capacitive, and conductive electron transfer mechanisms in pyrogenic carbon functioned as an electron snorkel, which facilitated extracellular electron transfer and stimulated soil alternative microbial respiration to suppress methane production. Our results highlight an important, but overlooked, function of pyrogenic carbon in neutralizing forest fire emissions and call for its consideration in the global carbon budget estimation. Warmer and drier conditions are increasing the frequency of forest fires, which in turn produce pyrogenic carbon. Here the authors show that accumulation of pyrogenic carbon can suppress post-fire methane production in northern peatlands and can effectively buffer fire-derived greenhouse gas emissions.

Automated summary

Recent studies have shown that the accumulation of pyrogenic carbon produced by forest fires in northern peatlands can effectively suppress post-fire methane production, providing a potential climate-cooling impact. The redox-cycling and electron transfer mechanisms in pyrogenic carbon play a key role in stimulating soil alternative microbial respiration to reduce methane emissions. This highlights the importance of considering pyrogenic carbon in global carbon budget estimation to mitigate the impact of forest fires on climate change.