Effect of changes in precipitation amounts and moisture sources on inter- and intra-annual stable oxygen isotope ratios (δ18O) of teak trees from northern Thailand

Abstract Thailand is situated in a transition zone of overlap between the Indian monsoon (IM) and the western North Pacific (WNP) monsoon. The region serves as an important area to study the influences of different moisture sources. This study presents the first stable oxygen isotope analysis on seven teak (Tectona grandis Linn.) trees collected from Phrae Province in northern Thailand at different temporal resolutions. Isotopic analyses of teak tree rings at both annual and sub-annual timescales reflected the variations in their source water oxygen isotope ratios (δ18O, i.e., rainfall) to different degrees (Annual scale: r = 0.31, p