人为干扰对川西北谢家山润楠次生林群落结构和物种多样性的影响

Effects of Anthropogenic Disturbance on Community Structure and Species Diversity of a Secondary Machilus nanmu Forest in Xiejia Mountain,Northwest Sichuan

采用典型样地法,对比研究重、中和轻3种强度人为干扰对谢家山润楠(Machilus nanmu)次生林群落结构和物种多样性的影响,采用物种丰富度指数(D)、Simpson优势度指数(H')、Shannon-Wienner多样性指数(H)和均匀度指数(JSW)来综合衡量群落的物种多样性水平。结果表明:(1)重度干扰群落各层次物种数最少。(2)不同强度人为干扰下润楠次生林的群落结构不同,轻度干扰群落中,在径级Ⅱ〔4.0 cm≤胸径(db,h)<8.0 cm〕出现数量峰值(74株);中度干扰群落中,在径级Ⅲ(8.0 cm≤db,h<12.0 cm)出现数量峰值(62株);重度干扰群落中,群落结构不稳定,在径级Ⅳ(12.0 cm≤db,h<16.0 cm)出现数量峰值(66株)。(3)随着干扰强度的增加,重要值集中在润楠、黄连木(Pistacia chinensis)和紫苏(Perilla frutescens)等少数物种上。(4)随着干扰强度的加强,灌木层和草本层物种多样性指数均先增加后减小,中度干扰群落灌木层和草本层物种多样性指数明显提高;乔木层各多样性指数均呈下降趋势。

Using the typical sample plot method,a comparative study was done of effects of anthropogenic disturbance varying in intensity,low,moderate and high,on community structure and species diversity of a secondary Machilus nanmu forest. Species richness index（ D）,Simpson dominance index（ H＇）,Shannon-Wienner diversity index（ H）,and Pielou evenness index（ JSW） of the forest were measured and used to evaluate comprehensively its level of species diversity. Results show that（ 1） plots of the forest under high anthropogenic disturbance were the lowest in number of species in various community level;（ 2） community structure varied within the forest with intensity of anthropogenic disturbance; and in the plot low in disturbance,trees,4. 0-8. 0 cm in DBH（ db,h）,peaked in number,reaching 74,while in the plot moderate in disturbance,trees,8. 0-12. 0 cm in db,h,did,reaching 62,and in the plot high in disturbance,trees,12. 0-16. 0 cm in db,h,did,reaching 66;（ 3） with intensifying disturbance,species importance value mainly concentrated on a few species,such as Machilus nanmu,Pistacia chinensis,and Perilla frutescens; and（ 4） with intensifying disturbance the biodiversity indices of shrub and herbaceous communities rose first and then declined,regardless of disturbance degree,but in the plot moderate in disturbance,they increased obviously,while the index of the tree community decreased in all plots.