雅安市谢家山两种密度柳杉人工林群落结构和物种多样性研究

Researches on Structure and Species Diversity of Cryptomeria fortunei Plantation under Two Kinds of Densities in Xiejiashan, Ya'an, Sichuan

林分密度是影响林分生长、群落结构及生物多样性的重要因素之一,对近自然森林的经营改造、森林生态系统稳定性的维持及林业可持续发展具有重要意义。为研究林分密度对群落结构和物种多样性的影响,并探索维持人工林生态系统的稳定性和促进近自然林业改造的合理林分密度,采用典型样地法,以物种丰富度指数D值、Shannon-wienner指数H值、Simpson优势度指数H′值和均匀度指数Jsw值作为综合衡量群落物种多样性的指标,对比研究了雅安市谢家山两种林分密度（高密度和低密度）对柳杉（Cryptomeria fortunei）人工林群落结构和物种多样性的影响。结果表明：（1）共记录到植物109种,隶属57科95属。高密度群落物种组成为乔木11种,灌木27种,草本41种;低密度群落物种组成为乔木17种,灌木35种,草本35种;（2）从群落结构上看,在高密度下,物种多分布在中径级（胸径11.0~23.0cm）和高高度级（高度15.0~24.0 m）;在低密度下,物种多分布在小、中径级（胸径5.0~23.0 cm）和小、中高度级（高度9.0~21.0 m）;（3）两种密度下群落的各指数均表现为：草本层〉灌木层〉乔木层。物种丰富度指数D值在乔木层和灌木层表现为低密度〉高密度,在草本层表现为低密度〈高密度。从Simpson指数H′值、Shannon-Wiener指数H值和均匀度指数值Jsw值分析来看,乔木层这些指数均表现为低密度〉高密度,而灌木和草本层则与之相反;研究认为低密度（1 250~1 375/（株·hm-2））更利于谢家山地区柳杉人工林多样性的维持及柳杉树种的自然更新。

Stand density, which is one of the key factors that influence stand growth, community structure and biodiversity, is significant in managements and reforms of close-to-nature forests, maintenances of the stability forest ecosystems and and the sustainable development of forestry. In order to investigate the effects of different density（high density and low density）on community structure and species diversity of Cryptomeria fortunei plantation in Xiejiashan mountain, Ya’an district, Sichuan province a field study was conducted. Four sample plots were selected in big and small density, respectively. The species richness index D, Shannon-wienner index H, Simpson index H′ and Pielou index Jsw were adopted to evaluate the level of species diversity in Cryptomeria fortunei plantation. The results indicated that： （1）A total of 109 species belonging to 57 families and 95 genera were founded in this study area. 11 trees, 27 shrubs and 41 herbs were included in communities of high density, and 17 trees, 35 shrubs and 35 herbs were included in communities of low density, respectively. （2）In terms of community structure, significant difference was found in communities of big and small density. Individuals under low density were distributed in small and medium diameter class （5.0~23.0 cm） and medium height class （9.0~21.0 m）. Individuals in high density were mainly distributed in medium diameter class （11.0~23.0 cm） and high height class（15.0~24.0 m）. （3）The species diversity at both low density and high density in different layers of these communities was in a decreasing order of herb layer＆gt;shrub layer＆gt;tree layer. The Species richness index D of the shrub layer and tree layer under the high density decreased, while it was converse in the herb layer. The Simpson index H′, Shannon-Wiener index H and Pielou index Jsw of the tree layer under high density increased, while they were converse in the shrub layer and herb layer.