Fire and vegetation dynamics in North-West Siberia during the last 60 years based on high-resolution remote sensing

Abstract. Rapidly warming Arctic undergoes transitions that can influence global carbon balance. One of the key processes is the shift towards plant species with higher biomass underlining a stronger carbon sink. The shift is predicted by the models based on abiotic climatic factors but it is not always confirmed with observations. Here we use high-resolution remote sensing to study the process of transition of tundra into forest on the 20 000 km2 area in North-West Siberia. Overall, 40 % of the study area was burned during 60-yr period. Three quarters of the burned areas were dry tundra. Ca 10 % of the study area experienced 2–3 fires with an interval of 15–60 years, suggesting a shorter fire return interval than that reported earlier for the northern areas of Central Siberia (130–350 years). Based on our results, the shift in vegetation (within the 60-years period) occurred in 40–85 % of the territories that experienced fires, suggesting a strong role of disturbances for the tree advance. All fire-affected territories were flat, therefore no effect of topography was detected. Oppositely, in the undisturbed areas, tundra-forest transition was observed only in 6–15 % of the territories, characterized by a steeper topographic slope. Our results show that the fires often originated near the centers of anthropogenic activity, which is continuously increasing due to the economic importance of the region. This might explain larger frequency of major fires in the northern territories of West Siberia compared to Central Siberia.