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 (Crypt omeria japonica D. Don) is difficult to explain by density alone. In this s tudy, 54 selected trees of 18 sugi cultivars, including eleven local cultiv ars and seven geographic races, were collected from one stand to investigat e 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 wid ely among cultivars, but these variations were small among individuals with in each cultivar. There was also a significant difference in density among cultivars, but it was smaller than for the Mf angle. Density variation amon g trees within each cultivar was relatively large in the geographic races. E-fr variation among cultivars was explained well by Mf angle characteristi cs in each cultivar, E-fr variation within each geographic race may be caus ed by density variation among trees.