Modeling the stem taper functions for Acacia hybrid in Dong Nai province

The objective of this study was to construct appropriate stem taper functions at the individual tree level of Acacia hybrid plantations. The stem taper functions were constructed from 150 sample trees at the age of 3 - 10 years in which their diameter at breast height ranged from 4 - 24 cm. The appropriate stem taper functions were constructed and tested from 2 forms of candidate functions. The form 1 was a multivariable stem taper function and form 2 was a single-variable stem taper function. The research results showed that the deviation of the multivariable outsidebark stem taper function was 19.0% and 42.2% smaller than that of the single-variable function of order 7 and order 2, respectively. Similarly, the deviation of the multivariable inside-bark stem taper function was 13.6% and 32.8% smaller than that of the single-variable stem taper function of order 7 and order 2, respectively. Accuracy of multi-order single-variable stem taper functions was improved by constructing for each diameter class.