Effects of microfibril angle and density on variation of modulus of elasticity of sugi (Cryptomeria japonica) logs among eighteen cultivars

The variation of dynamic modulus of elasticity values (E-fr) in sugi (Cryptomeria japonica D. Don) is difficult to explain by density alone. In this study, 54 selected trees of 18 sugi cultivars, including eleven local cultivars and seven geographic races, were collected from one stand to investigate the causes of the E-fr variation among cultivars. The results ranged from 3.63 to 9.93 GPa for E-fr of logs, from 3.4 to 59.4 degrees for rnicrofibril (Mf) angle in the S-2 layer of latewood tracheids and from 0.304 to 0.406 g/cm(3) in the air-dry density. The Mf angle values and their pattern of variation within a stem varied widely among cultivars, but these variations were small among individuals within each cultivar. There was also a significant difference in density among cultivars, but it was smaller than for the Mf angle. Density variation among trees within each cultivar was relatively large in the geographic races. E-fr variation among cultivars was explained well by Mf angle characteristics in each cultivar, E-fr variation within each geographic race may be caused by density variation among trees.