Post-fire vegetation phenology in Siberian burn scars

Abstract

Boreal forests comprise one third of global forested area and are the largest terrestrial carbon store. Forest fires are the regions most dynamic disturbance factor, occurring mainly in Siberia, Russian Far East, Canada and Alaska, and these fires represent a globally important release of terrestrial carbon to the atmosphere, via the burning of vegetation and organic soils. Currently the boreal region is believed to be a net carbon sink, but climate change predictions indicate significant boreal warming, with consequent increases in fire activity and carbon release. Ultimately, the boreal zone may become a net carbon source through forest fires and increased soil decomposition, and there is evidence that the Canadian forest may have already made this transition. Critical to estimating both direct and longer-term fire-related perturbations to boreal carbon storage is knowledge of fire extent, intensity and/or type, which has a strong control on forest fire damage, the fraction of available fuel combusted, and patterns of post-fire re-growth. These variables are currently derived from model-based assessment of often-uncertain accuracy, introducing large uncertainties to current carbon flux calculations. The post-fire re-growth process is of great importance since whilst fire releases carbon into the atmosphere, carbon sequestration through post-fire regeneration of plants and woody vegetation may help to reduce the amounts of carbon in the atmosphere. Observational data, such as vegetation indices, biophysical vegetation parameters, burnt area and fire radiative power, derived from satellite measurements are exploited to investigate post-fire regeneration and pre and post-fire temporal dynamics in the boreal forest. The relationship between post-fire dynamics and variables such as fire intensity, vegetation cover and climate are investigated. The ultimate aim of the proposed work is to improve insight into the Siberian boreal forest post-fire dynamics, leading to more realistic carbon flux quantification in the boreal biome and subsequently to a better quantitative understanding of the role of boreal forest regeneration in the global atmospheric carbon record.