Fire as a Major Factor in Dynamics of Tree-Growth and Stable δ13C and δ18O 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 (delta C-13(Cell), delta O-18(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 delta(18)OCell 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 delta C-13(Cell) values in tree rings from the two sites are positively correlated independently of the fire impact. This fact indicates that delta C-13(Cell) chronologies might be more adequate for climatic reconstruction in the region due to the climate signal consistency. Relationships of delta O-18(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).

Automated summary

Wildfires have a significant impact on forest ecosystem physiology and carbon balance in the permafrost zone of North Siberia. This study investigated the changes in tree-ring width and stable isotope chronologies of Larix Gmelinii after wildfires, revealing that tree-ring width and δ(18)OCell are the most sensitive parameters to the changing tree growth conditions. The study also showed the differences in the soil seasonal thermal regime after fires and the positive correlation of δC-13(Cell) values in tree rings between the two sites, suggesting the potential use of δC-13(Cell) chronologies for climatic reconstruction in the region. Furthermore, significant positive relationships of δO-18(Cell) values between the two sites were observed 60 years after the fire impact, indicating a long-term response of tree growth and isotopic ratios to climate changes.