Equations for predicting heartwood merchantable volume and tradable sawlog in tectona grandis

Heartwood is the most important part of the Tectona grandis tree. Although various equations for prediction of this tissue are available for this species, there are no models for prediction of its heartwood exclusively. The objective of the present study was to establish equations for predicting heartwood merchantable volume and tradable sawlog of teak trees growing in fast-growth plantations in Costa Rica. A total of 54 plantations were sampled from five regions of this country. Four equations were used to establish heartwood parameters using diameter at breast height (dbh), total height (H) and age as predictor variables. The equation selected for prediction of heartwood height (Hhw) and heartwood diameter (Dhw) included dbh and H. For Hhw, the equation proposed was Y = b1 + b2H + b3Age + b4dbh, with coefficients of determination (r2) of 0.87, while the stem profile equation to determine the different values of external diameter was dub = a0dbha1 Ha2XM with r = 0.94, and the equation to determine the Dhw was -4.83 + 0.190d, where d was any given external diameter of a tree. The selected equation could be used to predict total and commercial heartwood and quantity of sawlog of trees from plantation of T. grandis.