Abstract
Methods that can be used for predicting the merchantable volume produced from crooked trees have not yet been established. We developed a method that can be used to predict merchantable volume and volume ratios based on log grade. This method introduces a system of classifying stem crookedness into five classes using visual observation. Data from a total of 443 sugi stems were used to prepare equations for calculating merchantable volume and volume ratios based on log grade. The log grading rules employed here take into account defects such as crookedness, knots and decay and classify timber into three grades (i.e., A, B, and C) by which logs can be grouped according to length, diameter and crookedness. The merchantable volume equation uses stem crookedness classification as an explanatory variable and showed considerable improvement when compared to merchantable volume equations based on taper curve equations. The equations for volume ratio based on log grade could not well explain volume ratios of logs graded ‘A' or ‘B', but could explain volume ratios of logs graded ‘C' reasonably well. We confirmed that the models developed in this paper could predict log yield and revenue produced from crooked trees with reasonable accuracy.
