Heartwood formation and its relationship with basic density and green moisture content of young small-leaf mahogany trees

Swietenia mahogani (L.) Jacq. is one of Indonesia’s commercially valuable timbers. We investigated the time or age at which heartwood formation begins, and observed and determined whether the occurrence of heartwood formation was affected by age or diameter. The presence of heartwood from the bottom to the top (at various axial positions) of the stem was observed, and the basic density (BD) and green moisture content (GMC) were measured. The area of heartwood and sapwood was determined based on the colour differences in the cross-section. The results showed that the formation of the heartwood begins when the tree is four years old. In the axial position, the heartwood can be found in up to 65 of the tree height. The analysis of variance (ANOVA) test showed that heartwood proportion was determined more by diameter than by age. Therefore this can be a consideration for tree breeding programmes to select trees with larger diameters. Harvesting of young, fast-growing mahogany trees with large diameters from tree breeding can be expected to produce wood with good beauty and durability. Furthermore, BD in the heartwood was lower than in the sapwood, although there was a positive correlation between the proportion of heartwood and BD.