亚热带典型林分空间结构与林下草本物种多样性的差异特征分析及其关联度

Analysis of the difference and correlation between the spatial structure and understory herbaceous species diversity of typical subtropical forests

林分空间结构对林下草本物种多样性有显著的影响。为明确其影响林下草本物种多样性的主导因子,以亚热带杉木纯林、杉木混交林和天然次生林为研究对象,在量化分析3种林分的空间结构指数和林下草本物种多样性指数差异特征的基础上,采用灰色关联度分析林分空间结构和林下草本物种多样性的关系。结果表明:1)天然次生林的树种隔离程度、林层多样性、竞争态势和林木空间分布格局整体上最优,杉木混交林次之,杉木纯林最差。2)天然次生林、杉木混交林和杉木纯林的林下草本物种丰富度、Simpson多样性指数、Shannon-Wiener多样性指数、Simpson均匀性指数和Pielou均匀度5个指数都表现出天然次生林>杉木混交林>杉木纯林的规律。3)影响杉木纯林、杉木混交林和天然次生林林下草本物种多样性的共同空间结构因子是混交度。因此,欲提高杉木纯林和混交林的林下草本物种多样性,可选择通过改善树种结构的人为干扰措施来实现。

The spatial structure of a forest has a remarkable effect on the diversity of the understory herbaceous species. To clarify the dominant factors that affect the species diversity of understory herbaceous vegetation, a subtropical pure Chinese fir plantation, mixed Chinese fir plantation, and natural secondary forest were used. On the basis of the quantitative analysis of three kinds of stand spatial structure index and understory herbaceous species diversity index of different characteristics, the main spatial structure factors influencing the understory herbaceous species diversity were excavated using grey relational analysis. The results showed that: 1) In terms of the tree species isolation degree, forest layer diversity, competition situation, and forest spatial distribution pattern, the natural secondary forest was the best, followed by the mixed Chinese fir plantation and then the pure Chinese fir plantation. 2) In the five indexes of species richness (Simpson diversity, Shannon- Wiener diversity, Simpson evenness, and Pielou evenness), a regularity showed that natural secondary forest > mixed plantation > pure plantation. 3) The degree of mixing was the common key factor affecting the diversity of the understory herbaceous species in the pure Chinese fir plantation, mixed Chinese fir plantation, and natural secondary forest. Therefore, to improve the diversity of the understory herbaceous species in pure Chinese fir and mixed Chinese fir plantations, to some extent, it is acceptable to use artificial interference measures, such as regulating the tree species structure.