中文摘要：

确定合理的抚育强度有利于提高林分的健康性和稳定性,林下植被生长状况是衡量森林生态系统稳定性的重要指标,研究抚育强度与林下植物生长的关系对提高森林生态系统稳定性、改善林分生态条件有重要意义。以北京市侧柏人工幼龄林为研究对象,于2004年按照阳坡薄土、阳坡厚土和阴坡厚土3种立地条件设置了31块样地,并进行了弱度（20%）、中度（35%）和强度（50%）抚育,同时设置对照样地（0%）;于2005年和2009年调查了抚育后1 a和5 a的林下植物生长情况来分析各抚育强度对林下植物生长的影响。研究结果表明：林分郁闭度随抚育强度增强而降低;不同强度抚育后林下植物种数均增加,以中强度抚育后林分增幅最大;Simpson多样性指数、Shannon-Wiener多样性指数和Pielou均匀度指数均随抚育强度增大而增加,Shannon-Wiener指数对抚育措施更为敏感;灌木草本生物量随抚育强度增大而增加;综合分析可知,抚育造成的林分郁闭度降低及林下光照增加是林下植物生长势提高的重要因素。

英文摘要：

Rational thinning intensity is favorable to improving the forest health and stability.Growth condition of undergrowth vegetation is an important factor for weighting the forest ecosystem stability.Thinning was one of the major methods for improving the stability and growth conditions of forest ecosystem.Thirty one Platycladus orientalis young plantation stands in Beijing mountainous areas were selected in this study.The plots were divided into 3 site types which were sunny slope with thin soil,sunny slope with thick soil and shady slope with thick soil,and were set in 2004.The thinning intensities included low,medium,heavy and control with the cutting percents of 20%,35%,50% and 0%.The investigations were conducted in 2005 and 2009 for the purpose of researching the suitable thinning intensity and the growth changing of underground vegetation.The results showed that the crown density decreased with the thinning intensity,the variety of undergrowth species increased after thinning,and stand with middle and heavy thinning intensities had the highest increasing number.Simpson,Shannon-Wiener and Pielou indeces increased as the increase of thinning intensity,and Shannon-Wiener index was more sensitive to thinning.Biomasses of the undergrowth vegetations increased with thinning intensities.Generally speaking,the raising trend of growth potential of undergrowth vegetations was the result of the decreased crown density and the increased lighting after thinning.