Into the unknown: The role of post‐fire soil erosion in the carbon cycle.

Wildfires directly emit 2.1 Pg carbon (C) to the atmosphere annually. The net effect of wildfires on the C cycle, however, involves many interacting source and sink processes beyond these emissions from combustion. Among those, the role of post‐fire enhanced soil organic carbon (SOC) erosion as a C sink mechanism remains essentially unquantified. Wildfires can greatly enhance soil erosion due to the loss of protective vegetation cover and changes to soil structure and wettability. Post‐fire SOC erosion acts as a C sink when off‐site burial and stabilization of C eroded after a fire, together with the on‐site recovery of SOC content, exceed the C losses during its post‐fire transport. Here we synthesize published data on post‐fire SOC erosion and evaluate its overall potential to act as longer‐term C sink. To explore its quantitative importance, we also model its magnitude at continental scale using the 2017 wildfire season in Europe. Our estimations show that the C sink ability of SOC water erosion during the first post‐fire year could account for around 13% of the C emissions produced by wildland fires. This indicates that post‐fire SOC erosion is a quantitatively important process in the overall C balance of fires and highlights the need for more field data to further validate this initial assessment. [ABSTRACT FROM AUTHOR]