Maturation status and genetic improvement effects on growth 271

A field trial was initiated in 1986 to evaluate nursery methods for producing aged cuttings of varying physiological age (PA) from stool-beds. Seedlings and cuttings taken from 5-year-old Pinus radiata D.Don seedlings grown in the field were included as controls. Three seedlots of different genetic improvement levels from unimproved bulk seed (GF3) to control-pollinated seed from a seed orchard (GF21) were used to study differences in growth rate, tree form, and wood properties (density and acoustic velocity) between cuttings of five different physiological ages up to 5 years and seedlings, and any interaction between physiological age and levels of genetic improvement. Results showed no persistent long-term height growth differences, and by 4 years of age, any height differences were no longer significant. GF16 and GF21 plants had significantly larger diameters than GF3 plants at both 4 and 11 years of age. Also, seedlings (PA0), and cuttings from 1-year-old seedlings (PA1), had significantly larger diameters than PA5 cuttings from field-grown trees; the cuttings of othe