Variation in wood characteristics of 20-year-old half-sib families of Pinus radiata

Increment core samples were collected at breast height (1.4 m) from 20-year-old trees of 30 of the top-ranked wind-pollinated progenies from the '268 ' series of Pinus radiata D.Don plus trees, and their wood properties were examined. The objectives were to establish the extent of any possible shift in average wood properties caused by intensive selection for growth rate and stem straightness, and to estimate genetic parameters (variances, narrow-sense heritabilities, and genetic correlations). Samples were also collected from control trees, representing a "felling select " seedlot, within the same progeny trial. Properties examined included growth rate, wood density, and resin content (all by five-ring core segments), heartwood percentage and compression wood rating (whole cores), and tracheid length (outerwood only). Although wood density was variable (coefficient of variation about 0.07), the average for the progenies overall was almost identical to that of the control trees. On the other hand, there were slight indications that, along with the improved growth rate of the progenies, compression wood and heartwood resin content levels increased whereas tracheid length decreased. Heritability estimates for all the actual wood properties were high, ranging from 0.4 upwards, and coefficients of variation for resin content variables and heartwood content were very high (0.4 or higher), suggesting good prospects for genetic manipulation