Abstract:

Chinese Fir and poplar are very popular plantation species in China. Better understanding of the variability of mechanical properties within a tree will result in economic and effective utilization of these two species. The MOR(modulus of rupture), MOE(modulus of elasticity), compression strength parallel to grain, shear strength parallel to grain and wood density were studied. The results showed: The MOR, compression strength parallel to grain and wood density of Chinese Fir increased wavelike from butt to top while MOE decreased contrarily. They had no statistically significant difference (at 5% level) between heights. Outer wood had higher properties than core wood, and all physic-mechanical properties had a statistically significant (at 1% level) different between core wood and outer wood. Only the MOE of I-214 poplar wood increased steadily from pith to bark, and the MOR in north direction had the same trend. As to other physic-mechanical properties, the lowest value appeared in the transition section while the highest value appeared near the bark. All the physic-mechanical properties had a statistically significant (at 1% level) different between position from pith to bark. Shear strength of core wood was lower than outer wood in radial section, and there was a statistically significant (at 1% level) difference between core wood and outer wood, not only Chinese Fir but also I-214 poplar. On the other hand, the shear strength of core wood was a little higher than outer wood in tangential section, but they had no statistically significant difference. Wood density had positive linear relationship with other mechanical properties, so wood density proved to be a good predictor for wood quality.

Key words: Chinese Fir, I-214 poplar, plantation, mechanical properties, wood density