Occurrence of annual and intra-annual rings related to meteorological records in khasi pines of northern thailand and twentieth-century climate reconstruction

In order to project the climate fluctuations back to the past and predict the changes in the future, climate variability inducing annual and intra-annual ring formation in Khasi pines (Pinus kesiya) growing in northern Thailand was investigated and the past climate was reconstructed. Annual and intra-annual rings from several Khasi pines were identified using the techniques of cross-matching and cross-dating. All of the 88 wood core samples were successfully cross-dating with a 118-year growing period from AD 1898 to AD 2015. The annual growth was significantly affected by the mean temperature in April (r =-0.423) and total rainfall in March-April (r = 0.371). The equatorial sea surface temperature during August-November of the previous year also significantly stimulated the growth of these pines (r = 0.370). Regression analysis indicated that the maximum temperature influenced the formation of intra-annual rings and could explain 48.1% of the variance in the intra-annual rings. It was also found that the total rainfall during the summer period of March-April declined from 68.1 mm in AD 1898 to 54.1 mm in AD 2015 with the average of total rainfall of 60.4 mm in the period. The rainfall projected in AD 2065 was around 48.1 mm, while the mean temperature in April gradually increased from 30.10 °C in AD 1898 to 30.45 °C in AD 2015 with the average temperature of 30.33 °C and should continuously increase to 30.60 °C in AD 2065.