Variations of growth and wood traits in standing trees of the third-generation Acacia mangium families in Indonesia

The breeding of a fast-growing tree species, Acacia mangium Willd. has entered the third-generation cycle in Indonesia. To fulfill timber industry needs, wood traits, as well as growth traits, should be improved by conducting appropriate tree breeding programs for this species. In the present study, growth and wood traits were measured for the 10-year-old third-generation A. mangium from 40 half-sib families originating from four sub-lines from two provenances. The mean values of ten families in each sub-line ranged from 17.7 to 21.8 cm for stem diameter, 14.3 to 16.2 m for tree height, 3.60 to 3.77 km/s for stress-wave velocity, and 19.9 to 20.9 mm for Pilodyn penetration, respectively. The broad-sense heritability values in each sub-line ranged from 0.014 to 0.444 for stem diameter, 0.000 to 0.208 for tree height, 0.261 to 0.715 for stress-wave velocity, and 0.171 to 0.484 for Pilodyn penetration, respectively. These results suggested that families with higher density and Young's modulus of wood, suitable for solid wood production, can be selected from the third-generation A. mangium. Stem diameter significantly correlated with the other three measured traits, while phenotypic correlation coefficients between stem diameter and stress-wave velocity or Pilodyn penetration were very low. In addition, no significant phenotypic correlations were found between other measured traits. Furthermore, positive- or non-significant genetic correlations were found between growth and wood traits in all sub-lines. Thus, it is concluded that the selection of families with good growth characteristics will not always reduce the wood properties of this species.