Relationship between wood density, microfibril angle and stiffness in thinned and fertilized Pinus radiata

The relationships between wood anatomy in standing trees and the strength of boards were examined in Pinus radiata D. Don (thinned vs thinned and fertilized) at 2 contrasting sites. Fertilizer treatments were applied after mid-rotation thinning. Logs were taper sawn and boards, near the pre-treatment/post-treatment boundary, subjected to acoustic and strength assessment. Average wood property data from a 12-mm increment core obtained prior to harvest, was extracted from the relevant portion of the radius. In general, fertilizer resulted in lower density, higher microfibril angle (MFA) and slightly lower stiffness. However, stiffness was still relatively high as the affected wood was from the more mature portion of the radius. SilviScan density and MFA data were good predictors of stiffness. Acoustic measurements on boards were strongly correlated with board stiffness. Path analyses explained up to 45% of the variance in stiffness, as a function of estimated MOE and log sweep.