Winter-spring temperature reconstructed from tree-ring earlywood blue intensity in southern Anhui province of China

Abstract

Winter-spring coldness exerts strong impacts on socioeconomic activities and crop production in southeastern China. Tree-ring based temperature reconstructions in southeastern China provides a long context of current temperature change, still lack study in Anhui province. This study developed tree ring width (TRW), earlywood blue intensity (EWBI), latewood blue intensity (LWBI) and delta blue intensity (difference between EWBI and LWBI, ΔBI) chronologies using the tree rings of Pinus taiwanensis in Dalishan Mountain, southern Anhui province. The strongest correlation (r = 0.7, p < 0.05) is found between EWBI and current January–May mean temperature during 1955–2021. We thus reconstructed winter-spring (January–May) mean temperature from 1846 to 2021 using EWBI, which explained 49 % (adjust 48.2 %) of the instrumental variances. The reconstructed temperature series revealed a warm period (2004–2021) and two cold periods (1943–1945, 1948–1967). Comparisons of temperature series with surrounding areas show similar changes, particularly in line with warming trends after the 1940s. Winter-spring temperature in the subtropical zone is significantly positively correlated with SST of the tropical western Pacific and Indian Ocean regions, indicating temperature variation due to quasi-biennial oscillation (QBO), pacific decadal oscillation (PDO), or solar activity. In the reconstructed mean temperature series, it was found that it was affected by a total of 8 volcanic eruptions. The vector wind in lower troposphere analyses show that the extreme cold and warm years are not only related to the northeast wind (wind direction and strength) and tropical ocean temperature (SST), but also to the Tibetan Plateau cold high. The study result indicates the better application value of BI in the further study of subtropical tree rings.