Tree-ring based climate reconstruction and growth–climate analysis of Pinus kesiya Royle ex Gordon in Doi Khuntan National Park, northern Thailand

Abstract

Tree-ring analysis is a valuable tool for understanding long-term climate patterns and their influence on tree growth. This study investigates the climate-growth relationships of Khasi pine (Pinus kesiya Royle ex Gordon) in Doi Khuntan National Park, northern Thailand (at elevations of 850 to 1 035 m a.s.l.), to reconstruct past climate and inform forest management. Using 48 cross-dated increment cores, we developed an 83-year chronology (1936-2018). Standard dendrochronological methods and regression models were applied. The radial growth of P. kesiya was primarily influenced by moisture availability, showing significant positive correlations with March rainfall (r = 0.39, P < 0.01) and April-July relative humidity (r = 0.45, P < 0.01). Growth was negatively correlated with April-July mean temperature (r = -0.47, P < 0.01), indicating that warmer wet seasons induce stress. False-rings served as complementary intra-annual drought proxies, linked to cool-dry transitional periods. Multiple regression models explained 40.6% of radial growth variance and 65.6% of false-ring frequency variance. Reconstructed climate series revealed significant warming trends since the 1930s, most pronounced in April extreme minimum temperature, which increased by +0.98 °C over the study period (Mann-Kendall test, P < 0.01). These findings highlight the vulnerability of montane pine forests to increasing temperatures and atmospheric dryness, providing a multi-proxy baseline for climate change adaptation.