Pinus latteri, commonly known as Tenasserim pine or two-needle pine, is widely distributed across the tropics of Southeast Asia. Its growth is highly sensitive to year-to-year hydroclimate variabilities. Tree-ring data of this species serve as climate proxies and provide the opportunity for paleoclimate reconstruction.

In a study published in Palaeogeography, Palaeoclimatology, Palaeoecology, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences, using tree-ring width data of Pinus latteri from three sites in southern Laos, developed a regional composite chronology and reconstructed the hydroclimatic variability during 1885–2019.

Researchers found that the ring widths of the trees were negatively correlated with temperature and positively correlated with precipitation, self-calibrated Palmer Drought Severity Index (scPDSI), and Standardized Precipitation Evapotranspiration Index (SPEI) in both dry and wet seasons. Also, they found that tree-ring growth was mainly influenced by moisture conditions during the dry and wet seasons, and had a positive correlation with SPEI from March to August.

The March–August drought reconstruction for southern Laos showed an increasing frequency of extreme dry and wet years since the 1970s, and identified several dry and wet episodes in southern Laos over the past 135 years. Notably, prolonged droughts occurred on a decadal scale during 1896–1905, 1925–1936, 1952–1971, and 1979–1988, possibly linked to El Niño-Southern Oscillation (ENSO) activities.

Moreover, researchers found that hydroclimatic changes in southern Laos were negatively correlated with sea surface temperatures in the tropical Pacific and Indian Oceans, suggesting that these changes were driven by large-scale ocean–atmosphere circulations.

“Our findings suggest that the rising occurrence of extreme drought events, exacerbated by global warming, may lead to more intense meteorological droughts affecting forest ecosystems,” said FAN Zexin, a corresponding author of this study.

This study shows that tree-ring widths of Pinus latteri in southern Laos are an effective tool for studying long-term hydroclimatic variability in the region. Researchers recommend expanding the tree-ring network to enhance spatial and temporal coverage of climate proxies in regions Southeast Asia.