本文对9个尾叶桉、巨尾桉、尾巨桉无性系0.5~2.5年生试验林生长率、差异性及林分直径结构分析，发现林龄0.5~1.5 a是无性系树高生长高峰期，此时树高生长率达79.20%~96.27%，是林龄1.5~2.5 a树高生长率的3~4倍；林龄1.5~2.5 a时，各无性系林分胸径、树高、单株材积生长率分别为19.66%~25.67%、18.58%~27.96%、52.57%~62.54%，生长率最大的是E7号无性系(胸径、单株材积)和E6号无性系(树高)；秩次相关分析表明：各无性系胸径、单株材积生长量在不同林龄时排序变动不大，而无性系树高生长量排序在不同林龄时变动较大；差异性分析表明：无性系间胸径、树高、单株材积生长差异显著，但随林龄增加有差异减小趋势；林龄2.5年生时，E5号无性系胸径、单株材积生长量最大，分别达11.39 cm、0.0736 m3；各无性系林分树木径阶范围为6~14 cm或8~14 cm，以10 cm或12 cm径阶树木占最大比例，除E8号无性系外，其余8个无性系树木径阶分布总体上近似正态分布。%This study examined differences in growth rates and diameter classes among nine 0.5-to-2.5-year-old Eucalyptus urophylla and hybrid clones in experimental stands. The peak period of tree height growth occurred at 0.5-to-1.5-year-old (79.2% ~ 96.3%) and this was 3 to 4 times that at 1.5-to-2.5-year-old. Growth in diameter at breast height, tree height and individual tree volume were 19.7%~25.7%, 18.6% ~ 27.9% and 52.6% ~ 62.5% respectively at 1.5-to-2.5-year-old. The highest growth in diameter at breast height and individual tree volume was by clone E7, and the highest tree height growth rate was by clone E6; rank correlation analysis showed that growth rate of diameter at breast height and individual tree volume changed slightly at different ages between each clone, and growth rate of tree height changed greatly at different ages between each clone. There were significant differences among clones for diameter at breast height, tree height and individual tree volume, though differences tended to reduce as age increased. Clone E5 had the fastest growth among all clones with diameter at breast height of 11.4 cm and individual tree volume of 0.074 m3 at 2.5-year-old. The diameter at breast height of each clone were in the range of 6~14 cm or 8~14 cm, and with the highest proportions of diameter grades being 10 or 12 cm. The distribution of diameter grades within each clone appeared to be normally distributed, with the exception of clone E8.
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