Influence of initial planting spacing and genotype on microfibril angle, wood density, fibre properties and modulus of elasticity in Pinus radiata D. Don corewood

Pinus radiata D. Don trees from six clones, grown at initial spacings of 2500 stems ha −1 and 833 stems ha −1 were destructively harvested. For these trees wood properties were measured on radial slices sampled at a height of 1.4 m above the ground. Relative to wide spacing, close initial stand spacing significantly reduced microfibril angle (MFA) and ring width and significantly increased dynamic modulus of elasticity (MOE), fibre length, latewood percentage and cell wall thickness. Density and fibre width were not significantly different between spacing treatments. Examination of the influence of genetic population on wood properties indicated that genotype significantly influenced MFA, MOE and ring width. The key wood properties MFA, MOE and fibre length were regressed against tree diameter, height and stem slenderness. All three wood properties were most strongly correlated with stem slenderness. Multiple regression models developed for MFA, MOE and ring width accounted for respectively 62%, 81% and 58% of the variation in these variables. The following changes occurred in sampled properties with increasing ring number: MFA and ring width declined markedly; MOE and fibre length increased markedly; latewood percentage and cell wall thickness increased slightly; and density and fibre width did not show any radial trend.