# Wildfires in the Siberian Arctic
###### Abstract  
Wildfires are increasingly understood as an ecological driver within the entire Arctic biome. Arctic soils naturally store large quantities of \(C\), as peat has formed throughout the Holocene. For the Siberian Arctic, we used observations from the MODIS remote sensing instrument to document changes in frequency, geographic extent, and seasonal timing of wildfires as well as vegetation productivity (GPP, NPP, EVI). We also used correlation and regression analysis to identify environmental factors of temperature, precipitation, and lightning occurrence associated with these changes. For the Siberian Arctic as a whole, we found that the decadal frequency of wildfire tripled from the 2001-2010 to the 2011-2020 periods. Increased decadal frequency was accompanied by the increased extent of the burnt area by a factor of 2.6. This increase in fire frequency and extent was not uniform, with the greatest increase in western Siberia with no marked increase for the Siberian Far East. These changes were accompanied by the northward migration of the northern limit of wildfire occurrence and an increase in duration of the wildfire season. We found that annual fire frequency and the extent of burnt areas were related to various combinations of seasonal air temperature, precipitation, ground moisture, and lightning frequency. After fires, vegetation productivity rapidly recovered to pre-fire levels. The northward spread of wildfire into the tundra will release carbon long-stored as peat. The enhanced vegetation productivity, rapid recovery of carbon fixation for burnt areas and the northward migration of boreal forest tree species may offset that release and maintain the current status of the Siberian Arctic as a C sink. Increased wildfire and loss of permafrost may threaten ongoing settlement and industrialization, particularly for western Siberia. Article 2022 20202020 July 2022020 July 2022020 July 2022020 July 2022020 July 2022020 July 2022020 July 202202020 July 202202020 July 202202  
In Siberia, fire has long been the primary source of disturbance in vast taiga landscapes. However, wildfire is a recent driver for tundra ecosystem dynamics. During the 21 st century, wildfire frequency and the total area burnt have increased for northern forests and Arctic tundra. The fire return interval appears to have shortened from that reported earlier for northern areas (e.g., [7; 8]). Arctic fires coupled with atmospheric warming tend to transform tundra to shrublands [9] and have a potential to accelerate the northward expansion of forest cover [10; 11; 12]. Increased fire frequency may also be supported by increased frequency of lightning strikes due to atmospheric warming [13; 14; 15]. At northern latitudes, lightning strikes cause about 90% of fire ignitions [3]. Increased frequency of lightning within the boreal zone has the potential to further increase fire frequency throughout the Siberian Arctic [13; 14; 15]. The Siberian Arctic, especially the West Siberian forest-tundra and tundra ecoregions, largely consists of lowland tiaiga forests and wetlands that have accumulated C throughout the Holocene. The increased frequency of fires causes more damage and releases long-stored carbon into the atmosphere, thereby threatening to transform the high latitude territory from a C sink to a net source of atmospheric C. Increased atmospheric C has the potential to fuel a positive feedback loop resulting in increased fire frequency and warming (e.g., [16]). Alternatively, increased atmospheric CO\({}_{2}\) may provide a fertilization effect, increasing C fixation, and biomass production at high latitudes (e.g., [17; 18; 19; 20; 21]). Alongside that, warming promoted increased C fixation. Thus, tree ring analysis associated an increase in radial growth index for northern forests in Canada and Siberia attributed to atmospheric warming [22; 23; 24]. Potentially these effects, i.e., CO\({}_{2}\) fertilization and warming, may offset C loss from increased wildfire.