中文摘要：

使用25块标准地资料,尝试用美国的树冠调查指标对北京山区油松人工林进行初步调查探究,对4种林分密度（500、1000、1500、2000株9hm-2）同龄级（40～50a）油松人工林树冠因子的研究发现：北京山区油松人工林（40～50a）林分密度应控制在1500株·hm-2以下有利于树冠生长;对比分析3种立地条件（低山阴坡厚土、低山阴坡薄土、低山阳坡厚土）下树冠生长情况,结果表明：油松最适宜生长在阴坡厚土条件下;对不同林分密度、立地条件下树冠因子进行相关分析,发现林分密度与冠幅、树冠长度、树冠密度、树冠透光率呈显著负相关;立地条件与树冠透光率呈极显著负相关（相关系数为-0.997）,与其他指标相关性较低,说明林分密度对树冠生长的影响较立地条件更大,是影响树冠生长的重要因素,合理调整林分密度有利于树冠的生长。

英文摘要：

A survey on crown indexes for four kinds of planting density （500,1000,1500,or 2000 individuals per hectare） was conducted in Pinus tabulaeformis plantations within the same age class （40～50a） in Beijing Mountain area. Twenty-five sample plots were selected and investigated by the crown indexes applied in America. Results show that P. tabulaeformis plantation should be controlled at a density below 1500 individuals per hectare,which is conductive to the growth of crown. The growth statuses of crown under three kinds of site conditions （thick soil on shady slope at low mountain,thin soil on shady slope at low mountain,thick soil on sunny slope at low mountain） were analysed. The most appropriate site condition is thick soil on shady slope at low mountain. Correlation analysis indicated that stand density was significantly negatively correlated with crown width,crown length,crown density,and crown light exposure,while there was a highly significant negative correlation between site condition and crown light exposure and a insignificant correlation between site condition and other crown indexes,indicating that stand density has a greater impact on the growth of crown compared with site condition. Thus,stand density is an important factor,and rationally adjusting stand density is conducive to the growth of crown.