Influence of stocking on radial and longitudinal variation in modulus of elasticity, microfibril angle, and density in a 24-year-old Pinus radiata thinning trial

Detailed radial measurements of wood properties at four heights (0, 1.4, 5, and 20 m) were taken from 24-year-old Pinus radiata D. Don growing at four final crop stockings (200, 350, 500, and 1100 stems·ha–1). Using these measurements, the objectives of the study were to examine pith-to-bark trends at several heights to (i) determine how stocking influenced modulus of elasticity (MoE), wood density, and microfibril angle (MFA), (ii) quantify the relations among these properties and age at different stocking levels, and (iii) develop a graphical model for MoE across the stocking range. The influence of stocking on all wood properties was primarily expressed through a highly significant interaction between age and stocking. Wood properties in the highest stocking treatment diverged from those in the lowest stocking treatment at tree age 5 to reach a maximum difference of 92 kg·m–3 (488 vs. 580 kg·m–3) at tree age 18 for density, –5.7° (29.2° vs. 23.5°) at tree age 10 for MFA, and 5.1 GPa (12.1 vs. 17.2 GPa) at tree age 20 years for MoE. Graphical predictions from the model show greatest gains in MoE at high final crop stocking to occur over the lower part of the stem.