Cellulose oxygen isotopic composition of teak (Tectona grandis) collected from Java Island: a tool for dendrochronological and dendroclimatological analysis

The oxygen isotopic composition (δ18O) of tree-ring cellulose has been recognized as a powerful tool for dendroclimatological and dendrochronological investigations in Asia. Only a few studies of cellulose δ18O so far published, however, have been conducted in Indonesia, and the spatial coherence of cellulose δ18O has yet to be clarified. In this study we measured cellulose δ18O of teak (Tectona grandis) collected from four sites on Java Island to evaluate the similarity between the different teak δ18O values and the potential for using teak δ18O both as a climate proxy and as a tool for cross-dating. Cellulose δ18O time series of Javanese teaks were found to be significantly correlated in all of the comparisons between sites, even between sites separated by a distance as great as 400 km. While significant correlations did not appear in the ring width data between our samples (expressed population signal (EPS) = 0.64; Rbar = 0.23; sample depth = 10), they were found between the cellulose δ18O values (EPS = 0.89; Rbar = 0.58; sample depth = 10). These results suggest that teak δ18O variations have higher spatial coherence and might be a useful tool for cross-dating. A significant negative correlation was observed between cellulose δ18O and the relative humidity/precipitation during the rainy season, indicating that the cellulose δ18O of Javanese teak is an effective proxy for relative humidity/precipitation during the rainy season. Cellulose δ18O was found to be positively correlated with precipitation during the dry season preceding the growing season, whereas it showed no correlations with the temperature and Palmer Drought Severity Index (PDSI), the key constraints of δ18O on the Indochina Peninsula.