Chiang Mai Journal of Science

The aim of this research is to find the regularity in frequencies of diameter increment, and determine the relationship between tree age and fluctuations in radial increment of Pine trees (Pinus eldarica). In this direction, three normal pine trees from Kelardashat site (north of Iran) were selected. Disks were cut down at breast height, and the annual ring width in radial axis (1974-2008) was determined by Binocular system. The additive functional-autoregressive model is considered and semi-parametric method is proposed to forecast regression function. Furthermore, the method is applied for annual ring width prediction. The results showed that the nonlinear time series model is an efficient model for prediction of annual ring width.