Geophysical processes and biosphere: article

Аnnotation: For the first time we present the results of the tree-ring structure anomalies in Siberian larch wood from the upper treeline transect from western to eastern Russian part of Altai-Sayan Mountain region. Based on anatomical wood structure analysis of tree rings (frost, light and missing rings, and latewood density fluctuations) using a microscope allowed us to reveal four extreme events during the periods: AD 1783-1785, 1788-1789, 1812-1814, and the year of 1884, when severe cooling expanded for the whole Altai-Sayan region. Our results are in agreement with historical archives. Comparative analysis showed that date of extreme cooling events coincided with major volcanic eruptions (volcanic activity index VEI ≥ 4) such as Laki (AD 1783, VEI = 4), Asama (AD 1783, VEI = 4), Etna (AD 1787, VEI = 4), Sufrier (AD 1812, VEI = 4), Avu (AD 1812, VEI = 4), Suvandosedzima (AD 1813, VEI = 4), Krakatau (AD 1883, VEI = 6). However, trees from the Altai-Sayan regions do not respond to the major volcanic eruptions like Tambora (AD 1815, VEI = 7), Novarupta (AD 1912, VEI = 6), and Pinatubo (AD 1991, VEI = 6). This heterogeneous response of woody plants on the major volcanic eruptions 19th-20th centuries can be explained by location of the powerful volcanic eruptions and remote sulphur clouds from the northern part of the Central Asia, as well as reduced trees’ sensitivity from the upper treeline of Altai-Sayan Mountain region to volcanic eruptions due to 20th-century warming and shifting the temperature limit of woody vegetation distribution.