COMPARING WOOD DENSITY, HEARTWOOD PROPORTION AND BARK THICKNESS OF DIPLOID AND TRIPLOID ACACIA HYBRID CLONES IN VIETNAM

Selected triploid Acacia hybrid (A. mangium × A. auriculiformis) clones grow at similar rates to commercial diploid Acacia hybrid clones planted widely in Vietnam. We compared wood properties at age 3.8 years of two promising triploid clones and two commercial diploid clones grown at Tan An, south Vietnam and Cam Hieu, central Vietnam, using discs from five trees per clone sampled at five heights above ground from 1.3 to 7.5 m. Heartwood proportions were calculated from disc diameters and heartwood–sapwood boundaries. Basic densities of triploid and diploid clones were similar at Tan An (434– 491 kg m-3 at breast height). At Cam Hieu, where tree growth was slower, all densities were lower, and the triploid clones had lower densities than the diploid clones (359 and 378 compared with 407 and 447 kg m-3). Heartwood proportions at breast height (45 and 47%) and bark thickness (4.5 and 4.6 mm at breast height) of the two triploid clones were higher than those of the diploid clones (25 and 31%, and 3.7 and 3.7 mm respectively) at Tan An but triploids and diploids did not differ in these traits at Cam Hieu. Implications for wood processing and product value are considered.