Dynamics of moisture regime in the Selenga River downstream basin and its reconstruction from Pinus sylvestris tree-ring width chronology

Abstract

Regional tree-ring width chronology of the Scots pine (Pinus sylvestris) was developed from 8 sites in the forest-steppe belt situated in the foothills of the Selenga midlands. Moisture signal contained in this chro-nology allowed to receive tree-ring based linear regression reconstruction models for 1767-2015 of annual Au-gust-July regional precipitation sum and of mean annual water discharge of the Selenga River playing an im-portant role in the water balance of the Baikal Lake. Comparison of the smoothed series allowed to estimate long-term variation component of these moisture regime parameters with high precision. At the same time, regional drought indices are less correlated with pine radial growth, because they have contribution of the other environmental variables, which are much less reflected in the tree rings of the investigated pine forest stands. Reconstructed dynamic of the moisture regime parameters is supported by documental evident of many so-cially significant events in the regional history, such as crop failures caused by both droughts and floods, and catastrophic fire in the Irkutsk city in 1879. Also, dependence of the amount of precipitation in the study area on the atmospheric circulation in Central Asia was revealed to have common pattern with other regions: nega-tive relationship of precipitation with the development of large high atmospheric pressure area with its center in the Altai and Tien Shan mountains.