|スギ品種の材質特性を明らかにするための基礎的な知見を得ることを目的にして, この研究を始めた.まず,九州地方の代表的な在来スギ6品種すなわち,クモトオシ,ヤイチ,オビアカ,メアサ,ヤブクグリ,アヤスギについて,樹幹木部の組織･構造,および力学的性質の予備実験的な検討を行った.晩材率は,年輪幅が広い品種で小さく,年輪幅が狭い品種で大きいことがわかり,肥大生長の速さとのかかわりを認めた.容積密度数は年...輪幅が広い品種ほど小さく, 容積密度数の樹幹内分布は樹心部で大きく,樹幹外周部へ向かうに伴って小さくなり,また樹幹の下部から上部へ向かって大きくなる傾向がある.樹幹材積生長量が大きい品種ほど仮道管は長く,また,髄からの年輪番号の増加に伴って生じる仮道管長の増加割合いが大きく,形成層齢の仮道管長への影響が著しかった.仮道管の接線方向の直径･壁厚･壁圧比には,目立った品種間差異を認めなかった.樹幹材積生長量が大きい品種ほど,静的曲げヤング率,静的曲げ比例限応力度,縦圧縮ヤング率,縦圧縮比例限応力度が大きく,静的曲げ破壊仕事率,縦圧縮破壊仕事率,衝撃曲げ吸収エネルギーが小さかった.しかし,静的曲げ強さと縦圧縮強さには,品種間で際立った差を認めなかった.
The wood properties of Sugi (Cryptomeria japonica D. Don) were examined to determine the effects of differences in cultivars on the physical and mechanical properties. In this study six cuItivars which have been realised as the native clonal cultivars in Kyushu, the southernmost major island of Japan, were sampled from a 13-year-old stand. The results may be summarised as follows: I) Growth rate data for sample trees from a 13-year-old stand are shown in Table 1. 2) Late wood percentages of the fast-growing cultivars were less than those of the slow-growing cultivars. 3) Basic densities increased inwards and upwards in a stem, and the fastergrowing cultivars showed lower values on whole-stem basic density. 4) Tracheid lenghts of the fast-growing cultivars were longer than those of the slow-growing cuItivars. Tracheid length was highly dependent on the cambial age and this trend is remarkable in the fast-growing cultivars. 5) Six cultivars were comparable in tracheid diameter, wall thickness, and cell waIl percentage and insignificant difference can be measured statistically among cultivars. 6) There were not found remarkable differences in the static bending strength values among the cultivars. Young's modulus and fibre stress at the proportional limit in bending were higher for the fast-growing cultivars than for the slow-glowing cuItivars. On the other hand, work to ultimate load in static bending and absorbed energy in impact bending were lower for the fast-growing cultivars than for the slow-growing cultivars. 7) The results of the longitudinal compressive test showed similar tendencies to the results from static bending test. 8) Fractures occurred during bending are shown in Photo 1.続きを見る