Abstract
Wildfires are one of the main factors for landscape change in tundra ecosystems. In the absence of external mechanical impacts, tundra plant communities are relatively stable, even in the face of climatic changes. In our study, lichen cover was degraded on burnt tundra sites, which increased the permafrost thaw depth from 100 to 190 cm. In old fire scars (burnt 1980 – 1990) of the forest-tundra, vegetation cover was dominated by trees and shrubs. The soil temperature on burnt forest-tundra sites was higher in comparison to conditions of the unburnt control sites and permafrost was was not found at a depth of 2-2,3m. Dynamics of the Normalized Difference Vegetation index (NDVI) from 1986-2020 reveal that immediately after fires, vegetation recovered and biomass increased due to the development of Betula nana shrubs. In old fire scars of the forest-tundra (burnt 1980-1990), a significant increase in NDVI values was evident, in contrast to the unburnt tundra vegetation where this trend was less pronounced. We conclude that "greening" in the north of Western Siberia may occur due to fire-induced transformation processes. The role of wildfires in the advance of the treeline to the north, driven by climate change and active economic development of the Arctic, will gradually increase in future.
Highlights
Wildfires are an important environmental factor, strongly influencing structure and distribution of vegetation, the intensity of the carbon cycle, and properties of the upper soil layer
Betula nana dominates in the shrub layer (35% of the total cover), Vaccinium uliginosum is the dominating the dwarf shrub species (15% of the total cover), and a large part of the site is covered with Cladonia stellaris
On the second unburnt control site, situated at the southern border of the tundra zone (s.7) 85% of the total cover was occupied by Cladonia stellaris
Summary
Wildfires are an important environmental factor, strongly influencing structure and distribution of vegetation, the intensity of the carbon cycle, and properties of the upper soil layer. The frequency and intensity of tundra fires increase in direct proportion with anthropogenic impact, especially in areas of oil and gas production [3]. Even a single fire leads to strong changes in geochemical and geobotanical conditions of the Arctic landscape, which is characterised by low stability and a high potential of natural resources. Fire-induced changes in water regime, polar vegetation, and tundra and subboreal landscapes of the permafrost zone are the focus of very few studies [1]. The impact of fire on foresttundra in the face of climate warming and greening processes of the Arctic remains poorly studied [5, 6]
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