采用样方调查及取样分析方法,研究广西大青山南亚热带不同密度马尾松人工林林下植被及土壤特征.结果表明:马尾松人工林自然发育14 a后，林分密度从1050 株·hm-2增加到1800株·hm-2，林下灌木层物种多样性指数增高.密度为1800 株·hm-2时,多样性指数最高.当林分密度继续增大到2250 株·hm-2，灌木层物种多样性指数却呈降低趋势.林下草本物种多样性指数对林分密度变化的响应不敏感；在林分密度影响下，林下灌木生物量与灌木层物种多样性指数变化规律一致.随着林分密度的增大，林下草本生物量呈降低趋势；不同密度马尾松人工林土壤理化特性差异显著(P<0.05).除全K、速效K和速效P外，土壤表层(0～20 cm)养分含量与林下灌木层物种多样性指数变化趋势一致.不同密度林地速效K和速效P含量变化波动较大.密度为2100 株·hm-2的林分土壤
全P含量较高.中密度(1800 株·hm-2)林地的土壤持水量和孔隙度均较高，土壤容重较低.
By using plot investigation and sampling analysis methods, the understory vegetation and soil properties of Pinus massoniana plantations with diff
erent stand density in subtropical area were studied in Daqingshan, Guangxi Province. In the P. massoniana plantations after 14-year natural growth, the understory species diversity index of shrub layer increased with the increase of stand density from 1050 trees·hm-2 to 1800 trees·hm-2, but decreased when the stand density further increased to 2250 trees·hm-2. Herb species diversity index was not sensitive to the stand density change. With increasing stand density, shrub biomass had the same variation trend as that of shrub species diversity index, while herb biomass decreased with increasing stand density. Significant differences (P<0.05) were observed in the soil (0-20 cm) physical and chemical properties between the plantations with different stand density. The soil nutrient contents except those of total P and available K and P had the same variation trend with that of the understory species diversity index of shrub layer. Soil available K and P contents fluctuated with stand density, whereas soil total P content was higher when the stand density was 2100 trees·hm-2. In the plantations with moderate stand density (1800 trees·hm-2), soil waterholding capacity and soil porosity were higher, and soil bulk density was lower.