OXYGEN ISOTOPE (δ¹⁸O) OF TEAK TREE-RINGS IN NORTHWEST THAILAND

Abstract

We investigated the relationship between the oxygen isotopes in teak (Tectona grandis) tree-ring cellulose and climatic factors, i.e. rainfall, temperature and relative humidity. Four cores of teak from northwest Thailand were used to analyse the oxygen isotope values in α-cellulose. The oxygen isotopic composition of teak tree-ring α-cellulose ranged from 21.38‰ to 25.58‰. The mean tree-ring α-cellulose δ¹⁸O values and standard deviations were 23.4 ± 0.7‰. The δ¹⁸O value was positively correlated with rainfall in the February to April dry season (r = 0.234, p < 0.5) and negatively correlated with total rainfall (r = -0.350, p < 0.01), average rainfall (r = -0.321, p < 0.01) and relative humidity (r = -0.282, p < 0.05) in the late rainy season. The δ18O values were negatively correlated with the annual mean Palmer Drought Severity Index (PDSI) from 1948 to 2005 (r = -0.491, p < 0.001) based on the mean of 4 grids. Oxygen isotope values in the α-cellulose of teak from northwest Thailand were significantly related to the hydrological cycle in these areas.