Influence of Microfibril angle on within-tree variations in the Mechanical properties of chinese fir (Cunninghamia Lanceolata)

Radial variations in microfibril angle (MFA) and their effect on the mechanical properties of plantation-grown Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) were investigated with the aim of achieving an effective utilization of the wood. Correlations between MFA and mechanical properties, including longitudinal modulus of elasticity (MOEL), static bending strength (MOR) and compression strength parallel-to-the-grain (CS), were analyzed for predicting the quality of timber. The results indicated that MFA had a greater variation in juvenile wood than in mature wood. The biggest change occurred close to the pith in Chinese fir. The outer-rings (rings 9–30 from the pith) have a relatively low MFA, together with high mechanical properties and high density, when compared with the inner-rings (rings 1–8 from the pith). The MFA had significant negative curvilinear correlations with all the mechanical properties (MOEL, MOR and CS) of Chinese fir, with the value of r2 being 0.88, 0.69 and 0.74 respectively. The correlation between the MFA and basic density (BD) was strong in certain consecutive rings (rings 5–30 from the pith), but this did not apply across the whole billet, i.e. from the pith to the bark.