幼龄材范围的确定及树木生长速率对幼龄材生长量的影响

DIFFERENTIATION OF JUVENILE WOOD ZONE AND EFFECTOF TREE GROWTH RATE ON INCREMENTOF THE JUVENILE WOOE

本文以杉木、日本落叶松的人上林和天然林木材为对象，选择ｙ＝ａ＋ｂｌｎｘ回归模式。利用其管胞特征因子随年轮数的变化，研究划分幼龄材年轮界限的最适因子，并就生长速率对幼龄材生长量的影响进入了探讨。结果表明：杉木和日本落叶松的人工林及天然林木的管胞特征值在径向水平上的变化均遵循ｙ＝ａ＋ｂｌｎｘ模式，尤其管胞长度与年轮数回归的相关系数Ｒ均达０．９８以上；管胞长度与管胞宽度及纤丝用相比，遗传率最大，随年轮数变化的模式最稳定，是划分幼龄材界限的最佳因子，由此得出杉木人工林幼龄材界限年轮为２０－２２（距髓心距离为１２．９－１３．２ｃｍ）、天然林为１６－１８（４．１－４．５ｃｍ），日本落叶松人工林为１９－２３（８．７－１０．５ｃｍ）、天然林为２３－２４（２．９－３．１ｃｍ）；幼龄材生长量与树木生长速率成正比。

In order to disdnguish the juvenile wood from mature wood in plantation or natural forest of China fir (Cunninghamia lanceolata ) and Japanese larch (Larix kaempferi), a variation distribution of the averge tracheid feature value was applied to the logatithmical fonmula y = a +blnx, where y was the tracheid feature value (tracheid length, tracheid width and fibril angle), x was the ring number or dislance from the pith, and the effect of growth rate on the increment of juvenile wood were Studied. The results show that the regression curves oblanied from this logarithmical formula agreed well with the actual variation and the coefficient of correlation R between tracheid length and ring numher or distance from the pith (0.98), so the ratio among tracheid length, tracheid width and fibril angle was suitable to he used to differentiate the juvenile wood zone. Furhemore, the increasing rate in tracheid length of annual rings was estimaled by the regression curve ovtanied, and the juvenile and mature wood could be differentiated at the point of one percent of annual increasing rate in tratcheid length. It. was considered to he an effective method. The annual rings or distance from the pith of juvenile zone differentiated by this method ranged from 20 to 22 or 12.9- 13.2cm for plantation,from 16 to 18 or 4.1-4.5cm for natural forest of China fir,from 19 to 23 or 8.7- 10.5 for plantation and from 23 to 24 or 2.9-3. 1 cm for natural forest of Japanese larch respectively. The increment of juvenile wood was in direct proportion to the growth rate.