Temporal dynamics of vegetation indices for fires of various severities in southern Siberia

Wildfire is a critical environmental disturbance affecting forest dynamics, succession, and the carbon cycle in Siberian forests. In recent decades forests of southern and central Siberia experienced an increase in fire-disturbed area. The main goal of this study was to assess the degree of fire disturbance in the southern regions of central Siberia, as well as the dynamics of post-fire changes for fires of different intensity. Remote sensing data from MODIS and VIIRS sensors were used to estimate burned area, fire radiative power (FRP) and post-fire dynamics using Normalized Burn Ratio (NBR) and Normalized Difference Index Vegetation (NDVI). Mean annual burned area between 2001 and 2021 in the region was about 950 thousand ha per year with the largest burned areas observed in mixed and larch-dominant forests. Fires detected in the dark-needle coniferous (DNC) and larch-dominant forests were found to have higher (by about 25%) fire radiative power comparing to fires in pine-dominant and mixed forests. The analysis of FRP together with NBR showed a significant correlation (R = 0.68; p < 0.05) between these variables, indicating that fires with higher intensity generally result in higher degree of fire disturbance. Evaluation of the post-fire dynamics showed that NBR is more sensitive to fire-related disturbances comparing to NDVI and requires up to 20 years to return to pre-fire values. At the same time, the recovery of the NDVI to background values took about 7–10 years after the fire.

The study was supported by the Russian Science Foundation and the Government of Republic of Khakassia (grant #22-17-20012, https://rscf.ru/en/project/22-17-20012/).