Variation of Wood Properties with Height Position in the Stems of Obi-Sugi Cultivars

Abstract

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.

Microfibril angle and density of hinoki (Chamaecyparis obtusa) trees in 15 half-sib families in a progeny test stand in Kyushu, Japan

“…The variation of MFA in juvenile wood (average rings B10) was larger than the MFA of mature wood (average rings C11) and family characteristic MFA was clearer in juvenile wood. In sugi cultivars, the effect of MFA on MOE was larger where MFA B15° [20]. If this relationship also applies to hinoki, although mature wood MFA is less variable than juvenile wood MFA, the variation of mature wood MFA may be an important trait affecting overall mechanical properties of the timber.…”

“…As described before, in Douglas-fir (Pseudotsuga menziesii), density was the most contributor to MOE and MOR, and MFA was relatively unimportant [4]. In small clear specimens of sugi cultivars, the effect of MFA on MOE in longitudinal compression was larger than that of density [20]. In sugi timber, the effect of MFA on MOE in bending was larger than density [21].…”

“…In sugi timber, the effect of MFA on MOE in bending was larger than density [21]. MFA accounted for 80% of variation of MOE in compression of obi-sugi small clear specimens [20]. This implies the effect of density on mechanical properties is larger in hinoki than in sugi.…”

Large deflections of tapered cantilever beams made of axially functionally graded material

“…(Suzuki, 1948, Kamruzzaman, 2008. A similar tendency has been reported for other plants, notably Obi-sugi cultivars, which are a type of cedar tree (Tsushima et al, 2007, Kijidani andKitahara 2009) and slash pine (Li et al, 2007). Returning to bamboo, its properties mean that it has FG characteristics both radially and axially.…”

“…According to the experimental results of Suzuki (1948), Kamruzzaman (2008), and Kijidani et al(2009), Young's modulus is linearly proportional to bamboo or tree height. Hence, we assume that the cantilever beam is uniformly tapered and has a linearly varying Young's modulus.…”