Abstract
Yakushima-sugi woods have high potential as structural timber owing to having their high mechanical properties. However, the factors influencing the mechanical properties have not been investigated. In this study, the wood properties of 25-50 years old Yakushima-sugi trees grown at four locations in Yakushima, two locations in Tanegashima and one location in Togo district (Kagoshima) are determined.
The dynamic modulus of elasticity, the latewood percentage, and the basic density of Yakushima-sugi woods were higher than those of common sugi-woods. The woods with higher latewood percentages had bands of compression-wood like tracheids in the latewood. In addition, Yakushima-sugi woods had longer tracheids than common sugi-woods.
Both the basic density and the S2 microfibril angle affect the dynamic modulus of elasticity of Yakushima-sugi woods. There were differences in how these two factors affected the dynamic modulus of elasticity of Yakushima-sugi woods among sites. Higher basic density and/or lower S2 microfibril angle were the cause of the higher mechanical properties of Yakushima-sugi woods.
