We examined and simulated the consequences of the degradation of the litter and the moss–lichen layer after fire impact, which could affect the seasonal temperature of the soil and the depth of the seasonally thawed layer (STL) in the permafrost zone. According to the analysis of satellite imagery for 2000 to 2019, the fire-disturbed area in the region of interest amounted to 20%. The main aims of the study included quantitative evaluation of the variation range of summer temperature anomalies at fire-damaged plots, summarizing the statistical norm of the STL depending on natural conditions, and numerical simulation of the response of the STL. Using Terra and Aqua/MODIS imagery, we analyzed surface temperature (in bands of λ = 10.780–11.280 and 11.770–12.270 μm) coupled with the normalized difference vegetation index (NDVI) for non-disturbed and fire-damaged sites under the same natural conditions of larch forests in Central Siberia. Heat transfer, freezing and thawing processes were numerically simulated for two extreme cases of soil conditions: dry soil and water-saturated soil. The model was also applied to soil with non-homogeneous water content. As input parameters, we used data on the properties of cryogenic soils collected in larch forests (Larix gmelinii) in the flat-mountainous taiga region of the Evenkia (Central Siberia). For post-fire plots, surface temperature anomalies observed during summer months remained significant for more than 15–20 years after fire impact, while the NDVI values were restored to the statistical norm within 7–10 years of the fire. According to the results of numerical simulation, the thickness of the STL could show a 30–50% increase compared to the statistical norm. In the first approximation, we showed the annual soil temperature dynamics at various depths in disturbed and non-disturbed plots.

This study is based on the processing of satellite imagery in the wave range 3.93-3.99 μm (Terra/Modis satellite) and numerical simulation results. It has been found for combustion conditions in Siberian forests that the observed fire radiative power (FRP) is 15% of the total fire power. Variations between 10 and 30% depend on both the fire development scenario (specific burnup rate of 0.01-0.1 kg/m 2 s and fire front velocity of 0.01-0.1 m/s) and the conditions for remote imaging. Instrumental estimates for the ratio of fire areas by given intensity quantiles for Siberian forests are presented. The share of low-, medium-, and high-intensity fires is 41.2-58.9, 35.0-46.5, and 6.10-13.44% of the total area. Refined estimates of fire emissions have been obtained taking into account the amount of biomass burnt and variable burning intensity. The proposed method allows the mass of burned forest fuel materials (FFM) and direct fire emissions to be estimated quantitatively at a level 14-21% lower than the values calculated with the help of standard approaches. The estimates of direct carbon emissions in the given time interval of 2002-2016 were 83 ± 21 Tg/year on average, which is 17% lower than the value 112 ±25 Tg/year obtained with the standard method.

We investigated changes in the temperature regime of post-fire and post-technogenic cryogenic soils of Central Siberia using remote sensing data and results of numerical simulation. We have selected the time series of satellite data for two variants of plots with disturbed vegetation and on-ground cover: natural ecosystems of post-fire plots and post-technogenic plots with reclamation as well as dumps without reclamation. Surface thermal anomalies and temperature in soil horizons were evaluated from remote data and numerical simulation and compared with summarized experimental data. We estimated the influence of soil profile disturbances on the temperature anomalies forming on the surface and in soil horizons based on the results of heat transfer modeling in the soil profile. According to remote sensing data, within 20 years, the thermal insulation properties of the vegetation cover restore in the post-fire areas, and the relative temperature anomaly reaches the level of background values. In post-technogenic plots, conditions are more “contrast” comparing to the background, and the process of the thermal regime restoration takes a longer time (>60 years). Forming “neo-technogenic ecosystems” are distinct in special thermal regimes of soils that differ from the background ones both in reclamated and in non-reclamated plots. An assumption was made of the changes in the moisture content regime as the main factor causing the long-term existence of thermal anomalies in the upper soil horizons of disturbed plots. In addition, we discussed the formation of transition zones (“ecotones”) along the periphery of the disturbed plots due to horizontal heat transfer.

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