An analysis of fire characteristics in the boreal forests of Siberia (50–75° N, 60–140° E) was performed for the period 2002–2022. We found a positive trend in the proportion of high-intensity fires in dominant forest stands of Siberia based on long-term series of variations in the Fire Radiative Power (FRP) measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS). Our results showed that there was an increase in the proportion of areas of high-intensity fires over the past decade on about ~30% of the boreal forests of Siberia, including the Arctic zone. For the sample group of fires, the level of correlation (R² = 0.80–0.94) between the fire impact, classified according to the NBR/dNBR technology, and the integral FRP values was revealed. The intensity of combustion in terms of FRP is associated with the volume of burned biomass and determines the dynamics of specific emissions values per unit area. The results suggest that further increase in fire emissions in Siberia will be determined not only by an increase of burned areas, but also by a redistribution of low- and high-intensity burning and an increase in specific emission values. Finally, we estimated that Siberian fires are responsible for about 5–20% of the total volume of greenhouse gas emissions in the Russian Federation, depending on the fire season scenario. The recurrence of extremely high emissions (296–350 Tg C/year) will make it possible to consider part of Siberian forests as a source of carbon in the nearest future.

Wildfire in Siberia is extensive, affecting up to 15 Mha annually. The proportion of the vegetation affected by severe fires is yet unknown, and it is a problem that requires a solution because post-fire mortality of tree stands in Siberian taiga has a strong effect on the global budget of carbon. The impact of fire in our area of interest in eastern Siberia was analyzed using the normalized burn ratio (NBR) and its pre- versus post-fire difference (dNBR) applied to Landsat-8 (OLI) collected in 2020–2021. In this paper, we present the classification of fire impact in relation to dominant tree stands and vegetation types in boreal forests of eastern Siberia. The dNBR of post-fire plots ranged widely (0.30–0.60) in homogeneous larch (Larix sibirica, L. gmelinii) forests, pine (Pinus sylvestris) forests, dark coniferous stands (Pinus sibirica, Abies sibirica, Picea obovata), sparse larch stands, and Siberian dwarf pine (Pinus pumila) stands. We quantified the proportions of low, moderate, and high fire severity (37%, 39%, and 24% of the total area burned, respectively) in dense tree stands, which were varied to 30%, 57%, and 13%, respectively, for sparse stands and tundra vegetation dominated in the north of eastern Siberia. The proportion of severe fires varied according to the transition from dominant larch stands (33.2% of the area burned) to pine (12.6%) and dark coniferous (up to 26.4%). The current proportion of stand-replacement fires in eastern Siberia is 12–33%, depending on vegetation type and tree density, which is about 2500 thousand hectares in 2021 in the region. According to our findings, the “healthy/unburned vegetation” class was quantified as well at least 700 thousand hectares in 2021.

The impact of fire on the boreal forests of eastern Siberia was analyzed using the normalized burn ratio (NBR) and its pre- versus post-fire difference (dNBR) applied to Landsat-8/OLI data. We provided the classification of fire impact in relation to dominant tree stands and vegetation types. For post-fire areas of different disturbance levels, we evaluated the 5-year dynamics of restoration processes in terms of anomalies in the surface temperature (ΔT/T_bg, %) and in the Normalized Difference Vegetation Index (ΔNDVI/NDVI_bg, %), which can indirectly characterize the post-fire state of vegetation and recovery.

The article provides the results of analysis of the characteristics of wildfires in various predominant stands of Siberia (50°–75° N, 60°–150° E) based on satellite monitoring data from 2015 to 2021. Thirty-six fires were selected for seven types of different tree stands (vegetation types) with a total area of 19 382 km². Seventy-two images of the Landsat-8 OLI/TIRS (Operational Land Imager/Thermal Infrared Sensor) satellite were used in the analysis, as well as data from standard products of MODIS (Moderate Resolution Imaging Spectroradiometer). Based on the processing of remote data (threshold classification of dNBR (differenced normalized burn ratio)) values, statistical patterns of the ratio of disturbance classes for various types of tree stands were revealed. It is shown that, in the case of fires in light coniferous stands, the ratio of disturbance classes is on average 44, 29, and 27% for low, medium and high levels of fire impact, respectively. While this proportion is 63, 14 and 23% in the case of dark coniferous forests, and 59, 26, and 15% in the case of tundra vegetation, respectively. The conjugate analysis of the radiation power of active fire zones using the fire radiative power (FRP) technique demonstrated an increase in the intensity of fires in terms of integral FRP values, proportional to the increase in the degree of fire impact on vegetation. For a representative sample of fires (in various postfire polygons in seven variants of vegetation cover), a significant (R² = 0.77–0.94, p < 0.05) level of correlation was revealed between the values of the normalized burn ratio/differenced normalized burn ratio (NBR/dNBR) and the integral values of the FRP parameter. It has been instrumentally confirmed that high intensity fires (20 000–100 000 MW) are mainly recorded in light coniferous plantations, where the proportion of medium and high degree of fire impact is the greatest (~56%) as well. The results allow us to consider these indices as complementary when solving the problem of estimating the amount of burning biomass, for example, when calculating the volume of direct fire emissions.

The variability of heat emission from fires in Siberian larch stands (within the boundaries of 60°–65° N, 100°–130° E) was studied. We used the sample of the seven largest wildfires with a total area of 10 000 km² recorded in 2018, 2020, and 2021. For comparison, we analyzed a selection of wildfires recorded in 2015–2021 (29 fires, on a total area of up to 18 000 km²) with reference to other predominant variants of vegetation in Siberia: spars larch, stands of pine, spruce, Siberian pine (cedar), as well as tundra vegetation and Siberian dwarf pine (Pinus pumila). We operated with the data on radiation power from active combustion zones, calculated using the fire radiative power (FRP) method and standard MODIS products. It is pointed out that the relative burn area of larch stands (γ = 0.69%) exceeds by at least 2 times the same characteristic of other variants of vegetation in Siberia. It is shown that quasi-normal distribution of FRP values is typical for all large-scale fires (with area \( \gg \)20 km²) of Siberia, including fires in larch forests. FRP from fires in larch forests can range from 12 000 to >260 000 MW. At the same time, the sporadic extremes of integral FRP (FRP_int) are an order of magnitude higher than the values corresponding to other variants of vegetation. The average FRP per a pixel of MODIS for fires in larch forests are 15% higher than the ones for pine stands and 25–35% higher than the typical values for fires in dark coniferous forests. The relation of FRP_int with the area of active combustion is approximated by a linear function with a confidence of at least 0.6 (p < 0.05). At the same time, the value of FRP_int aggregated over the entire period of fire development depends logarithmically on the final burned area. Based on the dependence, it is possible to estimate the characteristic realization time of the three phases of wildfire dynamics not only in terms of burned area, but also using energy characteristics in terms of heat emission.