The climatic signal in tree rings of the common oak (<i>Quercus robur</i> L.) on the south-eastern border of its range in the Ural River basin, Russia

Aim. The objective of this study was to identify and analyze the climatic signal contained in the tree-rings of common oak on the southeastern border of its range in Russia (Ural River basin).

Material and Methods. The materials for the study were tree-rings in samples of common oak wood from three sites in the southern part of the Dziau-tyube ridge. Measurements of ring-width were performed on the MBS binocular microscope and on the Lintab measuring complex with the TSAP-WinTM software package. The construction of tree-ring chronologies was carried out in the ARSTAN program. Dendroclimatic analysis was carried out in the R package treeclim.

Results. The limiting climatic factors for the radial growth of the common oak on the southeastern border of its range are precipitation during the winter-spring season and the initial period of vegetation and to the greatest extent with the precipitation in March-May. It was shown that the strength of this climatic signal in oak tree rings was not constant over time. The dynamics of this signal are characterized by the presence of local periods of decline, the beginning of which is timed to the years of mass gypsy moth outbreaks.

Conclusions. Since the beginning of the 1980s, there has been a significant decrease in the relationship of radial growth with the amount of precipitation for March-May. The reason for this change, in our opinion, could be a strong change in the condition of trees and stands caused by the consistent impact of strong oak defoliation caused by Gypsy moths and late spring frosts.

Precipitation reconstruction for the northwestern Chinese Altay since 1760 indicates the drought signals of the northern part of inner Asia

Based on the significant positive correlations between the regional tree-ring width chronology and local climate data, the total precipitation of the previous July to the current June was reconstructed since AD 1760 for the northwestern Chinese Altay. The reconstruction model accounts for 40.7 % of the actual precipitation variance during the calibration period from 1959 to 2013. Wet conditions prevailed during the periods 1764-1777, 1784-1791, 1795-1805, 1829-1835, 1838-1846, 1850-1862, 1867-1872, 1907-1916, 1926-1931, 1935-1943, 1956-1961, 1968-1973, 1984-1997, and 2002-2006. Dry episodes occurred during 1760-1763, 1778-1783, 1792-1794, 1806-1828, 1836-1837, 1847-1849, 1863-1866, 1873-1906, 1917-1925, 1932-1934, 1944-1955, 1962-1967, 1974-1983, 1998-2001, and 2007-2012. The spectral analysis of the precipitation reconstruction shows the existence of some cycles (15.3, 4.5, 3.1, 2.7, and 2.1 years). The significant correlations with the gridded precipitation dataset revealed that the precipitation reconstruction represents the precipitation variation for a large area of the northern part of inner Asia. A comparison with the precipitation reconstruction from the southern Chinese Altay shows the high level of confidence for the precipitation reconstruction for the northwestern Chinese Altay. Precipitation variation of the northwestern Chinese Altay is positively correlated with sea surface temperatures in tropical oceans, suggesting a possible linkage of the precipitation variation of the northwestern Chinese Altay to the El Niño-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). The synoptic climatology analysis reveals that there is the relationship between anomalous atmospheric circulation and extreme climate events in the northwestern Chinese Altay.