Short-term effects of experimental fire on CO2, CH4 and N2O exchange in a well-drained arctic tundra

Wildfire frequency in the Arctic has increased in recent years and is projected to increase further with changes in climatic conditions due to warmer and drier summers. Yet, there is a lack of knowledge about the impacts such events may have on the net greenhouse gas (GHG) balances in ecosystems. During three consecutive growing seasons, we investigated the immediate and short-term effects of experimental fire on carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) surface fluxes in a well-drained tundra ecosystem in West Greenland. During the fire, we monitored litter and surface temperature, as well as the soil temperature in the top 0-5 cm. The results showed that surface temperatures exceeded 400 °C during the burning process and combusted all aboveground biomass, which significantly affected the ecosystem carbon (C) balance. Burned plots continued to be a net CO₂ source for at least two years after burning. Meanwhile, soil temperature did not exceed 60 °C during the fire, and soil GHG cycling appeared relatively resistant to these conditions. Burning had an effect on soil properties and CH₄ fluxes only immediately after the fire event and it had no significant effect on ecosystem respiration (ER). Instead net CH₄ uptake and ER correlated (p<0.05) with soil moisture and soil temperature, respectively. No significant fire effects were observed in net N₂O fluxes which suggests that processes linked to the nitrogen (N) cycle are driven by factors that were not affected by this moderate fire event.