Dendrochronological evidence of extreme droughts in the forest-steppe of Western Siberia

: Current climate models project an increased frequency and intensity of droughts in the Eurasian forest-steppe. Although forests in this area are at risk from increasing aridization, our understanding of the forest vegetation response to increasing drought stress remains limited. Here, we examined a network of 12 new tree-ring width (TRW) chronologies of Scots pine ( Pinus sylvestris L.) in the forest-steppe zone of Western Siberia to determine the effects of climate variability on tree radial growth. The data were generalized using principal component analysis (PCA) into three regional chronologies characterized by a diverse climatic signal. While the northern sites demonstrated a weak growth–climate response, TRW at the southern sites strongly correlated with the six-month standardized precipitation evapotranspiration index (SPEI6) in February–July ( r = 0.65, p < 0.001). Based on this relationship, we defined the years with the extremely low summer SPEI6 (July) in the southern forest-steppe of Western Siberia for the period from 1850 to 2020. Our reconstruction identified the most severe droughts during the last two centuries in 1851, 1890, 1904, 1911, 1931, 1952, 1975–1977, 1989, 2004, 2010, and 2012. These results indicate the increasing effect of drought stress on Scots pine populations along the aridity gradient in the forest-steppe ecotone, emphasizing the potential vulnerability of trees under changing climate.