Genetic variation in commercial properties of six and fifteen year-old Eucalyptus globulus.

Solid wood properties were measured on samples cut from two progeny trials of Eucalyptus globulus: a six-year-old trial of later generation controlled-pollinated progeny; and a 15-year-old provenance-progeny trial of first generation open-pollinated natural stand collections. Both stands had been grown under fibre-production management without early thinning and pruning. Tree size, stem sweep, and branch score was assessed, a subset of trees felled (34 age-6 and 253 age-15 trees) and1.5-metre-long mini-sawlogs were harvested from a height of two metres. Back-sawn and quarter-sawn boards were cut from the mini sawlogs with portable sawmills. Whilst the sample sizes were relatively small and thus estimates of variances and heritabilities somewhat dubious, we observed apparent exploitable genetic variation in most traits. Growth, branch score and spring in green quarter-sawn boards showed significant between-subrace and probably within-subrace genetic variation. Bark thickness showed only between-subrace variance, and stem sweep showed only within-subrace genetic variation. Wood colour may have a low heritability but only very low additive variance, and cup in backsawn boards appeared to have a high degree of additive variance but very low heritability. No genetic variation in taper was observed.