Reconstruction of hydroclimate variability in southern Laos from 1885 to 2019 based on Pinus latteri tree-ring data

Abstract

The climate of Southeast Asia is influenced by the Asian monsoon systems, and inter-annual hydroclimate variability exerts a significant impact on forest ecosystems and agricultural productivity in this region. To improve our understanding of long-term drought variability, this study established ring-width chronologies for Pinus latteri trees at three sites in southern Laos. Site chronologies show negative correlations with temperature and positive correlations with precipitation, the self-calibrated Palmer Drought Severity Index (scPDSI), and the Standardized Precipitation-Evapotranspiration Index (SPEI) during the dry and wet months. The regional composite chronology shows the strongest correlation (r = 0.657, p < 0.001) with SPEI during March–August, indicating that the radial growth of P. latteri in southern Laos is primarily influenced by moisture conditions during the dry-to-wet season. A well-calibrated regression model was employed to reconstruct the variability of March–August SPEI for the period 1885–2019, explaining 43.1 % of the observed SPEI variance during the calibration period 1960–2019. The reconstruction records inter-annual to decadal-scale drought variability in southern Laos including eleven extreme dry years and seven extreme wet years. Notably, the frequency of extreme dry and wet events has increased since the 1970s. The reconstruction shows spectral peaks with periodicities of 2.3–3.1 years and displays negative correlations with sea surface temperatures (SSTs) in the tropical Pacific and Indian oceans, indicating that hydroclimatic variations in southern Laos are driven by large-scale ocean-atmospheric circulations.