Wood Preperities of Plantation Sugi (Cryptomeria japonica D. Don) Trees : On cv. Kumotohshi and cv. Yabukuguri

この研究では,形成される木部の性質と林木の生長経過を関連させて検討することを目的にしている.そこで,生長が速いことで知られているクモトオシと生長が比較的遅いことで知られているヤブクグリを選び,その樹幹内木部の性質を比較検討した.容積密度数は,生長が遅い個体ほど大きい一般的傾向が認められた.仮道管長は生長が速い個体ほど大きい値を示している.年輪の周囲長の増大率が仮道管長に与える影響を求めたところ,周囲長の増大率が小さいものほど仮道管長の増加傾向が著しく, この傾向は周囲長の増大率が10%以下のとき特に著しかった.なお,年輪の周囲長の増大率の大小のいずれにかかわらず,クモトオシがヤブクグリよりも長い仮道管を持ち,品種内での個体差はほとんど認められなかった.すなわち,仮道管長には品種特性が著しいようである.生長が遠い品種であるクモトオシに対して,横断面内の年輪数から未熟材率を推定する曲線が得られた.In this study the effect of growth rate on wood properties of Sugi (Cryptomeria japonica D. Don) were examined, and the intrinsic properties of cv. Kumotohshi, the fast-growing cultivar, were compared to cv. Yabukuguri,the slower-growing cultivar. Basic densities obtained of the fast-growing sample trrees are slightly lower than those of the slow-growing sample trees within/between cultivars. Basic density values increase inwards and upwards in a stem. The longer tracheid are found in the fast-growing trees than in the slower-growing trees within/between cultivars as shown in Fig. 8. The tracheid length is plotted against the girth iricreasing rate to discuss the effect of pseudotransverse cell division of cambial illitial on the tracheid length as shown in Fig. 9. As the result inconsiderable differences are found within a cultivar, although differences are significant between cultivars. lt may be assumed that the hereditary effect on tracheid length is much important. Tracheid length increases outwards from the pith and attains the constant values at near the 10th annual ring from the pith at each of stem level as shown in Fig. 8. Hence it may be assumed that the juvenile wood is realised as the wood formed between from the pith to the 10 th annual ring. The juvenile wood percentages are plotted against the annual ring number from pith at given stem levels and are shown in Fig. 10