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In many tree breeding programs, plus trees have been selected according to growth rate or stern form in trees. Trees that have a high growth rate or good stern form do not always produce industrially desirable wood. Therefore criteria for wood quality should be considered in tree breeding programs. The objective of this study is to obtain the basic knowledge for breeding for wood quality in Paraserianthes falcataria, an important commercial tree species of Indonesia. Variation in the growth, log properties, basic density, and fiber length in 13-year-old P. falcataria was investigated. Even though all trees were the same age, diameter at breast height showed high variation, indicating a significant variance in the growth rate of seedlings. Significant differences in the log properties (green density, dynamic Young's modulus, and stress-wave velocity) were observed among the trees. Basic density showed a constant value up to 10 cm from pith, at which point it began to increase. The fiber length increased up to 10 cm from the pith and then showed an almost constant value. According to the radial variation of the basic density and fiber length, wood is categorized as core wood, which includes that up to 10 cm from the pith, and outer wood, which is that from 10 cm to the bark. In addition, a significant difference in the basic density of core wood was observed among the trees, indicating that the selection of a plus tree with high-density wood in this species is possible at a relatively early stage. These results indicate that the wood quality in P. falcataria can be improved through tree breeding.

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This study evaluated the wood properties of 5- and 7-year-old Acacia mangium trees planted in West Java, Indonesia. A plot (20 by 20 m) was selected in each stand. The stem diameter and stress-wave velocity (SWV) were measured for all trees (n = 24 and 18 for 5- and 7-y-old trees, respectively) in the plots. Core samples were taken from all trees in each plot using an increment borer to measure the basic density (BD) and compressive strength parallel to the grain (CS). The mean ± standard deviation stem diameter was 13.1 ± 3.0 and 21.9 ± 3.8 cm in 5- and 7-year-old trees, respectively. There was no significant correlation between stem diameter and SWV. The mean BD and CS for 5-year-old trees were 0.42 ± 0.02 g cm−3 and 30.0 ± 4.4 MPa, respectively, and for 7-year-old trees were 0.45 ± 0.02 g cm−3 and 32.8 ± 3.6 MPa, respectively. There was a positive correlation between BD and CS in 5- and 7-year-old trees (r = 0.790 and 0.583, respectively). The radial variation patterns for BD and CS were similar in 5- and 7-year-old trees: BD and CS gradually increased to about 6 cm from the pith, after which it was almost constant toward the bark. The results suggest that xylem maturation depends on the growth diameter in A. mangium.