To promote the use of sugi woods, the information on the variation of wood properties is very important. Obisugi is a major group of sugi cultivars planted in Southern Kyushu. However there is no information on the variation of wood properties with height position in the stems of Obi-sugi trees. We examined in detail the difference between the wood properties at 5 m above ground upper height position and those at 1.5 m above ground lower height position of Obi-sugi cultivars. Obtained results were as follows : Mechanical properties in both mature and juvenile wood at the upper height position were higher than those at the lower height position in most cultivars. Radial variations of mechanical properties at the upper height position were larger than those at the lower height position in most cultivars. Microfibril angle of latewood tracheids MFA in both mature and juvenile wood at the upper height position was smaller than those at the lower height position in most cultivars. On the other hand, basic density and latewood tracheid length in both mature and juvenile wood at the upper height position did not differ from those at the lower height position in many cultivars. Higher mechanical properties at the upper height position were mainly the result of the decrease of MFA with height position. In addition, to examine the whole tree variation from top to bottom, we investigated the variation of wood properties of Obi-sugi trees at different height increments. The results suggested that longitudinal variations of mechanical properties were well explained by variations of MFA and basic density, and that height increment affected the mechanical properties and the longitudinal variation pattern of wood properties. Keywords :Obi-sugi cultivars, wood property variation, microfibril angle, basic density, height increment.

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It was previously believed in Japan that the wood qualities of hinoki (Chamaecyparis obtusa) were superior to sugi (Cryptomeria japonica). However, few studies of wood properties such as MFA (microfibril angle of S 2 layer in secondary wall of tracheid) have been completed for hinoki. Some reports have found that hinoki plus tree families have similar mechanical properties to sugi. Here we report the characteristics of MFA and density of hinoki half-sib families in a progeny test stand. There were significant differences in MFA and density between families. The wood properties of two families, Nakatsu 3 and Kanzaki 5, are stable in radial pattern and suitable for structural use. Early selection of hinoki families by MFA and density may be difficult. Effects of MFA and density on E d (dynamic modulus of elasticity) of logs differed between families. The effects of growth rate on MFA and density differed between families and also between juvenile and mature wood. The faster growth rate in Nakatsu 3 appeared to improve wood properties and increase E d of logs, although in many other families, faster growth rate had negative effects on desirable wood properties for structural use.

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Using electronic strain gauges, longitudinal peripheral growth strain was measured at 1.6 m height in fifty 22-year-old plantation grown trees of Eucalyptus grandis (Hill) Maiden.The extent of peripheral growth strain was not found to be related to rate of growth. This result and measurements of internal growth strains in five 32-year-old trees suggested that splitting of wood during conversion would be less likely in trees with faster rates of growth, due to a lower longitudinal strain gradient along a radius from pith to outer xylem.