Comparative Reaction of Larch (Larix sibirica Ledeb.) Radial Increment on Climate Change in the Forest Steppe and Highlands of Southern Siberia

The influence of climate changes on larch (Larix sibirica Ledeb.) radial increment under conditions of a limited (forest steppe) and sufficient (high-altitude Kuznetsk Alatau, floodplain stands) humidification is considered. The relationship between growth index of larch trees (N = 257) and ecological and climatic variables is analyzed. In the forest steppe, with the onset of warming, a decrease in the aridity of the climate, an increase in the duration of the growing season (1980s), and an increase in the larch growth index followed by its depression in the 1990s have been observed. Radial-increment depression is caused by an increase in vapor-pressure deficit and arid climate due to a rising air temperature. In the 2000s, radial-increment fluctuations with average values not exceeding those before the beginning of current climate warming period occurred. In the highlands, since the 1970s, there has been a general increase in the larch radial increment closely associated with the main limiting factor of growth—air temperature. At the same time, in arid years, the radial-increment depression of larch trees in highland and floodplain larch forests is also noted. When implementing “hard” climate scenarios (RCP 6.0 and RCP 8.5), it is likely that the larch growth index in a forest steppe will decrease further and its increase in areas of sufficient moisture will be observed.