Effect of growing site on the fundamental wood properties of natural hybrid clones of Acacia in Vietnam

We investigated clonal and site variations in wood fiber length, microfibril angle, and specific gravity of seven natural hybrid clones of Acacia (Acacia mangium × Acacia auriculiformis) grown in northern and southern Vietnam. Fiber length did not differ between clones or between sites. The microfibril angle of the S₂ layer did not significantly differ between clones but significantly differed between sites. Clone and site significantly affected specific gravity. The significant effects of genetic × environmental interactions on wood properties indicated the difference in the response of clones to different growing conditions. The trends of changes in fiber length, microfibril angle, and specific gravity from the vicinity of the pith to near the bark were similar for all clones at each site; however, variations in fiber length, microfibril angle, and specific gravity were more visible in northern Vietnam than in southern Vietnam, with a significant effect of genetic factors. This difference may be attributable to winter, which is experienced in northern Vietnam but not in southern Vietnam. For clone selection for plantation in the northern region, combining growth rate with wood properties was recommended. On the other hand, for plantation in the southern region, clone selection depends mainly on the growth rate, taking into consideration the specific gravity.