林分密度对毛乌素沙地樟子松人工林林分结构和林下植被的影响

[目的]研究不同密度下,樟子松人工林林分结构和林下物种多样性的变化,以期为毛乌素沙地以樟子松为建群种的植物固沙模式提供理论依据。[方法]以毛乌素沙地榆林地区5种不同密度25a生樟子松人工林为研究对象,采用样方调查和测试分析法,探究樟子松人工林林分结构和林下物种多样性随林分密度的变化特征。[结果]樟子松人工林密度与平均胸径呈幂函数递减关系,与高径比呈显著的线性正相关关系。樟子松人工林林下共出现植物8科13属16种。草本以禾本科的狗尾草为优势种,草本丰富度、多样性指数随着密度的不断减小,表现出明显的增加趋势。林分密度与物种丰富度指数、多样性指数呈显著的负相关关系,Shannon多样性指数对密度变化最为敏感。[结论]毛乌素沙地樟子松人工林的林分密度与林分结构、林下物种多样性的相关关系十分显著,可以将林下物种多样性指数作为衡量林分密度是否合理的参考指标。

Effects of Stand Density on Stand Structure and Understory Vegetation of Pinus Sylvestris Plantations in Mu Us Sandland

[Objective] Pinus sylvestris is considered to be one of the preferred coniferous species in the Mu Us sandland afforestation. Studying the effect of stand density on the stand structure and understory vegetation development in order to provide important support for the stabilization of sands by afforestation in this region.[Methods] We selected the Pinus sylvestris plantations of 25 years old at different densities in Yulin City, and analyzed the changes in plantation structure and understory species diversity of Pinus sylvestris plantations with variations in stand density.[Results] The results showed the stand density and average diameter followed exponential relationship. And the height to diameter ratio showed a significant positive linear correlation with stand density. A total of 16 understory plant species were recorded, belonging to 13 genera and 8 families. Gramineae of foxtail grass was dominant species. Herbal species richness and diversity index showed an obvious increasing trend with decreasing density. The stand density was negatively correlated with the species richness and diversity index. Shannon diversity index was the most sensitive to changes in density.[Conclusion] In the management of Pinus sylvestris plantations in Mu Us sandland, the understory species diversity index can be seen as an indicator of the suitability of stand density.