Study on the species diversity of undergrowth in the different stand densities of Pinus tabulaeformis plantation of Xiaolongshan area | 小陇山林区不同密度油松人工林林下物种多样性研究

chinois. 研究油松人工林密度对林下植物多样性的影响及二者的关系，提出维持植物多样性、人工林生态系统稳定性及其健康状况的合理林分密度。以小陇山林区5种不同密度30年生油松人工林为研究对象，分析油松人工林林下物种的重要值、丰富度指数、多样性指数、均匀度指数和相似系数随林分密度的变化规律。①油松人工林林下共出现植物23科38属50种。随着林分密度的增大，林下物种数逐渐减少，灌木、草本层物种组成发生变化。②不同密度油松林林下灌木层和草本层植物丰富度指数、多样性指数，随林分密度的增加基本表现出减小趋势。③各指数与林分密度的相关性分析表明，灌木层和草本层的丰富度指数、草本层的均匀度指数与林分密度均表现出较高的相关性，其中草本层均匀度指数与密度呈显著负相关关系。④随着林分密度的增大，林下共有物种减少，相似系数逐渐降低。密度对人工油松林林下植物多样性有一定影响，但未达到显著水平；密度为1 717～1 867 株/hm2时，林下物种丰富度指数、多样性指数、Alatalo指数均达到最高，表明此密度是林下植被生长发育较为合适的密度，能够保障林下植物多样性的维持。

anglais. This paper studied the influence of stand density on species diversity of undergrowth of Pinus tabulaeformis plantation in Xiaolongshan area, to put forward an appropriate stand density. Five types of 30 years stand density were selected, and the law of important values, species richness, species diversity index, evenness index and similarity coefficient changing with stand density were analyzed. ① There were 50 vascular species in 38 families and 23 genus of undergrowth in P. tabulaeformis. As stand density increased, species number decreased, and the composition of shrub and herb changed. ② Species richness, Shannon-Wiener, Simpson index in shrub layer and herb layer deceased. ③ Correlation coefficient analysis showed that the stand density had some relationship with species richness and the evenness index of herb layer, which had significantly negative correlation with the stand density. ④ As stand density increased, the total forest loss of species, and similarity index gradually decreased. Analysis showed that stand density did have influence on species diversity, but the influence was no significant. When stand density was 1 717-1 867 plant/hm2, species diversity index except that Alatalo reached the highest, which indicated that the density was more appropriate for growth and development of understory vegetation, and can contribute to an increase in forest diversity.