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The distributions of forest, ice and snow in the Hengduan Mountains of China have undergone significant changes due to ongoing climatic warming. To better understand the spatiotemporal pattern of temperature changes in the Hengduan Mountains, we used tree-ring cores collected from multiple individuals of Larix speciosa Cheng et Law at five sites to develop a regional chronology and to establish the relationship between tree-ring radial growth and warm-season (May–September) mean temperature. The regional chronology accounts for 46.1% of the observed variance in the warm season and was used to reconstruct regional temperature levels back to 1420. Four cool intervals (1490–1570, 1590–1660, 1700–1790, and 1800–1880) indicate that the Western Hengduan Mountains experienced the Little Ice Age, and the changes were synchronous with cooling on the Tibetan Plateau and in the Northern Hemisphere, demonstrating a well-defined Little Ice Age signal in the South Asian monsoon region. Air–sea interactions and solar activity affected the variability of the warm-season mean temperature variations on interannual or interdecadal scales. Our temperature reconstruction improves the understanding of multi-centennial climate change in the Western Hengduan Mountains and has implications for advancing high-resolution paleoclimate science in the region. [ABSTRACT FROM AUTHOR]

In recent times, the warming and humidification of the Tibetan Plateau have become more pronounced. However, research on soil moisture on the Tibetan Plateau has been limited by the late initiation of data acquisition, thereby constraining the study of its driving mechanisms. Hence, there is an urgent need for historical time series to fill this research gap. To address this issue, we analyzed four spruce (Picea likiangensis) chronologies collected in high-altitude regions of the Tibetan Plateau, and we found that soil moisture during the dry season was a critical limiting factor for tree growth. The first principal component of a principal component analysis, accounting for 56.21% of the variance in all chronologies, was then used to reconstruct soil moisture variations from October of the previous year to May of the current year in the southeastern Tibetan Plateau from 1778 to 2020. We found significant relationships between soil moisture changes and the El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Variability (AMV). We also found a strong linkage between dry season soil moisture and summer temperature, suggesting that this relationship contributes to the intensification of warming and humidification on the Tibetan Plateau. • Tree rings provide a soil moisture record of the southeastern Tibetan Plateau since 1778 CE. • The reconstruction of soil moisture has demonstrated a close connection with large-scale climatic circulation patterns. • Coupling b/t soil moisture & temp boosts warming & humidification on Tibetan Plateau. [ABSTRACT FROM AUTHOR]