Radial growth response of Pinus sylvestris var. mongolica to drought at different elevations in northern Daxing'anling and reconstruction of the SPEI sequence

Abstract

In order to study the historical wet and dry changes in the northern Daxing'anling region of China, this paper established a standard chronology of tree-ring width at high (1150 m), medium (800–900 m), and low (700 m) elevations. The analysis was based on tree-ring cores of Pinus sylvestris var. mongolica from three elevation gradients in the northern Daxing'anling and correlates it with the SPEI (Standardized precipitation evapotranspiration index) of 12-month time scale. The established widths were correlated with the SPEI at a 12-month time scale. Climate-growth correlation analysis revealed that the low elevation chronology exhibited the highest correlation with the SPEI index in July–August (r = 0.665, p < 0.01). Based on this, a linear regression model between the low elevation tree-ring width chronology and the July–August SPEI index was established via regression analysis to reconstruct the dry and wet changes in the study area in the past 210 years. The explained variance (R2) of the reconstructed equation was 44.3%, (the explained variance after adjusting for degrees of freedom was 43.3%), and the F-value was 45.295.The reconstruction satisfied required statistical calibration and validation tests. The inter-annual variations indicate that the study area experienced six wet periods (1809–1818, 1828–1837, 1848–1864, 1928–1948, 1950–1972 and 1996–2003) and six dry periods (1819–1827, 1838–1847, 1865–1904, 1906–1923, 1973–1988 and 2004–2018), with an equal share of wet and dry years (13.8% and 14.8%). The reconstruction results are confirmed by the historical data and the reconstruction results of the surrounding region of the study area. Wavelet analysis reveals oscillatory cycles of 18, 26–29, and 40 years in the reconstructed sequence, which may be related to the North Atlantic Sea Surface Temperature Multi-Year Intergenerational Oscillation (AMO) and the North Atlantic Oscillation (NAO).