Climatic aspect of fir (Abies sibirica Ledeb.) mortality in the Eastern Sayan Mountains

The study considers the climatic response of fir (Abies sibirica Ledeb.) radial increment in the zones of dark coniferous decline on the northern spurs of the Eastern Sayan Mountains. Radial increment of 203 fir trees was analyzed. The measurement of the tree ring width and the development of tree-ring chronologies were carried out according to the generally recognized dendrochronological methods. The individual tree-ring chronologies obtained were divided into two groups according to the characteristics of the vital state of trees and radial increment trends over the past decades. It was found that significant differences in radial increment were observed after the drought in 1999. Comparison of the radial increment indices with the SPEI showed that the depression in radial increment coincide with a decrease in the level of atmospheric moisture and an increase in the sensitivity of trees to atmospheric droughts. Atmospheric drought, which caused a decrease in radial increment, also preceded an increase in fir mortality and an outbreak of Polygraphus proximus Blandford.