Fire as a Major Factor in Dynamics of Tree-Growth and Stable δ 13 C and δ 18 O Variations in Larch in the Permafrost Zone.

Wildfires are one of the most important environmental factors controlling forest ecosystem physiology and the carbon balance in the permafrost zone of North Siberia. We investigated tree-ring width (TRW) and stable isotope chronologies in tree-ring cellulose (δ¹³C_Cell, δ¹⁸O_Cell) of Larix Gmelinii (Rupr.) Rupr. from a wet (WS) and a dry (DS) site. These sites are characterized by different fire histories (fire in 1852 at the wet and 1896 at the dry sites, respectively). TRW and δ¹⁸OCell are identified to be the most sensitive parameters in the changing tree growth conditions after fire. The differences in the soil seasonal thermal regime of sites after fires are shown in the relationship between the studied parameters. The δ¹³C_Cell values in tree rings from the two sites are positively correlated independently of the fire impact. This fact indicates that δ¹³C_Cell chronologies might be more adequate for climatic reconstruction in the region due to the climate signal consistency. Relationships of δ¹⁸O_Cell values between the two sites are still significantly positive 60 years after the fire impact. Dendroclimatic analysis indicates significant changes in tree-ring growth and isotopic ratio responses to climate due to the increased demand of water for trees during the post-fire period (deeper seasonal subsidence of permafrost). [ABSTRACT FROM AUTHOR]