Abstract:
The relative importance of density, acoustic velocity, and microfibril angle (MFA) for the prediction of the stiffness (MOE) and strength (MOR) has not been well established for Douglas-fir (Pseudotsuga menziesii). MOE and MOR of small clear specimens of mature wood were better predicted by density and velocity than by either variable alone (183 trees >20 years old, 6 specimens/tree, 1087 specimens total). Specimens sampled around the stem circumference had similar density (intra-class correlation coefficient t=0.74), but not MOE (t=0.40) or acoustic velocity (t=0.32), indicating benefits from sampling several circumferential positions. For MOE, the path coefficients (β) were moderate for density and velocity. For MOR, β was only high for density. End-matched samples of one specimen per tree were analyzed with SilviScan. Simple correlations with MOE were highest for density (r=0.67), then acoustic velocity2 (0.53), MFA (-0.50), earlywood (EW) MFA (-0.45), and latewood (LW) proportion (0.40). Most correlations were weaker for MOR. Density had a higher β than did MFA for either MOE or MOR. In more complex path models, LW proportion and LW density were the most important contributors to MOE and MOR, and MFA was relatively unimportant. The path analyses showed what simple correlation did not: that LW proportion has strong predictive value for Douglas-fir mature wood quality.
Description:
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