PREDICTION OF STEM VOLUME OF ALSTONIA MACROPHYLLA GROWING AS EVEN-AGED MONOCULTURES USING DIAMETER AT BREAST HEIGHT AND TOTAL HEIGHT

Abstract

A growth model to predict the stem volume of Alstonia macrophylla was constructed in this study using data collected from 23 plantations from Galle, Matara, Ratnapura and Kalutara districts. Trees own variables were mainly used as explanatory variables in this study and in addition, site quality indices were also tested. At the preliminary analysis, two different site quality types were identified for the selected plantations. Therefore, first, each site quality data set was separately fitted to the theoretical models developed in this study. The selected models indicated a high modelling efficiency and a negligible bias. Although the possibility of using a common model for both site types was tested, results proved that it was not possible. Therefore it was decided to recommend two models (same structure with different sets of statistical parameters) for two site types for the field use  with the help of a given guideline to identify the plantations grown in two site types.