Effect of age on genetic control of Pinus radiata earlywood and latewood properties

Narrow sense heritability (NSH), and parental breeding values (PBV), of den sity, tracheid (fibre) radial and tangential diameters and stem growth in a small 4 by 4 radiata pine diallel were studied as a function of age using SilviScan-1 (a combined scanning X-ray densitometer and automated image ana lysis system). The earlywood/latewood boundary was set at a density of 500 kg m(-3). Earlywood properties were moderately to strongly inherited (NSH = 0.3 to 0.6) from a young age and latewood properties, other than tangentia l tracheid diameter, were more weakly inherited (NSH = 0 to 0.6), We sugges t that earlywood properties can be selected early in radiate pine and that physicomechanical properties of the growth ring depend to a large extent on those of the earlywood in this species. Significance of the results is discussed with particular references to refi ning behaviour and to sawn timber properties.