Increased drought sensitivity results in a declining tree growth of Pinus latteri in Northeastern Thailand

Abstract

© 2020 by the authors. Climate change may lead to alterations in tree growth and carbon cycling. Interpreting the response of forest growth to climate change requires an understanding of the temporal and spatial patterns of seasonal climatic influences on the growth of tree species. However, the effects of climate change on pine forest dynamics in tropical region of Thailand remain poorly understood. This study develops three new tree ring-width chronologies of Pinus latteri (Tenasserim pine) in northern and northeastern Thailand and analyzes their climate-growth relationships and temporal stability. Ring-width chronologies of P. latteri at three sites showed significantly positive correlations with precipitation, relative humidity and self-calibrated Palmer Drought Severity Index (scPDSI) during the dry season (previous November to current April) and early rainy season (May-June). Conversely, significantly negative correlations were found between ring-width site chronologies and air temperatures (mean, maximum and minimum) from April to August. Therefore, our results revealed that radial growth of Tenasserim pines from northern and northeastern Thailand was mainly limited by moisture availability during the dry-to-wet transition season from April to June. Moving correlations revealed that Tenasserim pines in the lowland area of northeastern Thailand became more sensitive to moisture availability in recent 30 years (1985-2017) as compared with early period (1951-1984). Accompanying the shifted growth sensitivity to climate change, growth synchrony among trees was increasing and tree growth rates of Tenasserim pines have been declining during recent decades at two more moisture-limited sites in northeastern Thailand. Recent rapid warming and increasing drought during the transition season (April-June) together intensify climatic constrains on tree growth of Tenasserim pines in the lowland area of northeastern Thailand. Considering continued regional climate change, pine forests in tropical lowland areas may encounter intensified drought stresses, and thus, become more vulnerable to future climate change. Our results serve as an early indicator of potential effects of climate change on tropical pine species and raise concerns about sustainable managements of pine forests under a changing climate.