Identifying the limits to fire growth in Eastern Siberia

Boreal forests store about one third of the world’s forest carbon and may store even more carbon in the future because of the positive effects of rising atmospheric CO₂ concentrations on photosynthesis and plant growth. However, fire frequency and severity have also been increasing in boreal forests in the last decades, which might offset their carbon sink potential. In Eastern Siberia, the dry and hot summers of 2020 and 2021 showed exceptionally high fire activity. However, even large fires that can spread for several months, eventually come to an end. This can be because of a change in the weather or because fires run out of fuels. Here, we aim to quantify the controls of fire growth in Eastern Siberia using high resolution landscape variables and hourly ERA-5 meteorological variables. We harmonized the burned area product from the Fire Climate Change Initiative and active fire product from the Visible Infrared Imaging Radiometer Suite, and derived fire perimeters from them for the period between 2012 and 2021. Along these fire perimeters, we then identified spatial changes in landscape variables (i.e. a decline in tree cover or increase in surface water) and temporal changes in hourly vapor pressure deficit and wind. By doing so, we could attribute causes of why fires stopped spreading.