南九州産スギ材の材質 ＩＩ―オビスギ品種の材質特性―

Abstract

The information on wood properties of sugi cultivars (Cryptomeria japonica) is very important for efficient use of sugi wood. Obi-sugi is a major group of sugi cultivars planted in Southern Kyusyu. However, the wood properties of Obi-sugi still have remained unclear. Therefore, the wood properties of 33-year-old Obi-sugi (15 cultivars) grown at one stand were determined. Mechanical properties were investigated by dynamic testing method for logs and compression test parallel to the grain for small clear specimens. In addition, basic density, latewood tracheid length and microfibril angle of middle layer in secondary wall (S2) in both earlywood and latewood tracheid were examinedThere were differences in the mechanical and anatomical properties of Obi-sugi among cultivars. The maximum and minimum values of static modulus of elasticity (Es) of the mature wood among the cultivars were 13.0 Gpa and 6.6 Gpa respectively. The patterns of radial variation in Es of the wood from pith to bark were also characterized by the cultivars. It was suggested that these revealed characteristics of the cultivars are quite essential information to decide the suitable end use of Obi-sugi.Both the basic density and the S2 microfibril angle affected the mechanical properties of Obi-sugi. Higher basic density and/or lower S2 microfibril angle were the cause of the higher mechanical performance of mature wood of the cultivars. S2 microfibril angle was also the most effective factor in both mature and juvenile wood.