Fire Damage to Boreal Forests of Siberia Estimated Based on the dNBR Index

The impact of fire on dominant tree stands in 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). We preprocessed satellite data on burned plots for 2015–2021. In result, 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. The proportions were varied to 30%, 57%, and 13%, respectively, for sparse stands and tundra vegetation dominated in the north of eastern Siberia. We estimated proportion of stand-replacement fires in eastern Siberia by 12–33% of total burned areas, depending on vegetation type and tree density.

Next, for post-fire areas of different disturbance level, we evaluated the dynamics of restoration processes through the ranges of anomalies in the surface temperature and the Normalized Difference Vegetation Index (NDVI). It is shown that the long-term dynamics of NDVI anomalies and average surface temperatures can indirectly characterize the post-fire state of vegetation and recovery. At the same time, it is necessary to take into account both the degree of fire impact and the type of dominant tree stand.