Tree-ring based minimum temperature reconstruction on the southeastern Tibetan Plateau

Increases in the annual minimum temperature (Tmin) has been more obvious than the increase in the annual mean temperature in the southeastern Tibetan Plateau (TP) over the past few decades; however, annual Tmin variability over the long-term in the southeastern TP has received scant attention. Here, we present a 413-year long tree-ring width chronology (TRW), which is composed of 22 site chronologies at high altitudes at the Hengduan Mountains on the southeastern TP. Climate-tree growth relationship analysis revealed that annual Tmin was the climatic factor that influenced radial tree growth in the area the most (R = 0.74, P < 0.001). Accordingly, we reconstructed the annual Tmin over the 1600-2012 AD period on the southeastern TP. The linear regression model between TRW chronology and annual Tmin accounted for 54.3% of the total variance in actual Tmin during the common period, 1960-2012. The close coupling of warm and cold episodes with other temperature reconstructions from surrounding regions indicated the reliability of our reconstruction. In addition, the comparison of reconstructed series with Climate Research Unit gridded data demonstrated that our reconstruction could represent the large-scale variability in annual Tmin on the TP. Furthermore, the Tmin variability exhibited similar trends with the temperature reconstructions from the TP, Asia, and northern hemisphere during the common period (1600-2012), indicating that the thermal variation in southeastern TP was consistent with the continental and hemispheric scale climate system variabilities. Atlantic Multi-Decadal Oscillation (AMO) and solar activity were observed to be key factors influencing annual Tmin variation over the southeastern TP. The results of the moving correlation analyses implied that the radial forest growth at high altitudes on the southeastern TP remained consistent with regional Tmin variation, and the decrease in precipitation has not yet limited forest growth. (C) 2020 Elsevier Ltd. All rights reserved.