<正>研究了两个杨树无性系（I-69杨和I-72杨）各生物组分中大量元素年变化规律。结果表明：两个无性系的大量元素在其各生物组分中的含量相近，变化规律相似；两个杨树无性系营养元素氮、磷、钾、钙、镁均以叶中元素含量的年变化幅度最为明显，分别为82.6%、82.2%、84.7%、85.7%和88.7%；当年生小枝与2年生小枝积累大量元素的规律相似；各生物组分生长最旺盛的时期存在养分的“稀释效应”；氮、磷、钾的平均含量以叶中最大，钙、镁以当年生木质部最大。研究结果可为杨树人工林的营养管理和地力维护提供依据。

The stands of 17-year-old Manglietia yuyuanensis Law. mixed with Chinese fir were researched by analysing the relationship between crown characteristics and growth of M. yuyuanensis Law. The results showed that the stemwood growth index(VI) was positively related to the total leaf area(TLA), surface area of crown(TCA) and crown shape ratio (CSR), but negatively related to the leaf area index(LAI) and crown layer density(CLD). The path analysis showed that TCA had the biggest direct effect(Pyxi=1. 201 3)on the stemwood growth. In the five main growth parameters of crown layer, based on the importance of relationships with stemwood growth, the order of them was TCA, LAI, TLA, CSR and CLD. The effects of spatial configuration of crown and stemwood growth were analysed. It showed that in the vertical distribution of crown foliage, the down and middle layer was decisive to the stemwood growth, the role of upper layers was secondary. In the horizontal distribution, inner and outer parts had the great contribution to the growth, but the middle parts had less. The study of reasonable crown structure of M. yuyuanensis could be used to. direct the big timber cultivation of M. yuyuanensis.