人为干扰对川西金凤山楠木次生林群落结构和物种多样性的影响

Effects of human disturbance on species diversity of Phoebe zhennan communitis in Jinfengshan Moutain in western Sichuan

物种多样性是群落功能复杂性和稳定性的重要量度指标,人为干扰对森林群落的影响可以通过群落结构和物种多样性的变化直接表现出来,不同干扰强度下群落结构和多样性特征不同。金凤山景区主要有选择性采伐和旅游活动这两种人为干扰形式,为研究不同强度人为干扰对金凤山楠木次生林群落的多样性和稳定性的影响,在实地充分考察的基础上,将干扰强度划分为3个等级:重度干扰:紧靠核心景区0—40 m,中度干扰:距离核心景区40—80 m,轻度干扰:远离核心景区80—120 m,采用典型取样法,调查3种不同强度的人为干扰对群落不同林分层次的物种组成、群落结构和多样性的影响,采用物种丰富度指数S值、Shannon-Wienner指数H值、Simpson优势度指数D值和均匀度指数Jsw值来综合衡量群落的物种多样性水平。结果表明:(1)在总面积为3600 m2的9个样地中,共记录到维管束植物155种,隶属于69科136属;物种数随着人为干扰强度增加呈递减趋势,轻度、中度和重度干扰下群落的物种数依次为:113种,88种,77种。(2)从群落结构上看,轻度和中度干扰下乔木个体多分布在小中径级(4<胸径DBH<20 cm)和低中高度级(5<高度H<13 m);而重度干扰下乔木个体多分布在小径级(DBH<8 cm)、大径级(DBH≥28 cm)和低高度级(3<H<7 m)、高高度级(H≥15 m),其群落结构与轻度和中度干扰下乔木层的群落结构明显不同。(3)受不同强度人为干扰的楠木次生林群落各物种多样性指数大小排序为:轻度干扰>中度干扰>重度干扰,S值、H值和Jsw随着人为干扰强度的增加而降低。

Over the last century,human disturbance plays an important role in the change of global climate and environment and consequently,the loss of global species diversity. Unsustainable use of forest resources is causing dramatic changes in the forest communities and poses a serious threat to biodiversity worldwide. Plant species diversity is an index reflects the complexity and stability of forest community function. The effect of human disturbance on forest community can be directlyreflected by the change of community structure and diversity. We hypothesize that community structure and plant species diversity vary with the different densities of human disturbance. In our study site in Jinfengshan Mountain,a tourism region located in Ya'an district,Sichuan Province,there are two major types of human disturbances: irrational selective cutting and tourism activities. In order to investigate the influences of different disturbances on the characteristics of species composition and diversity of Phoebe zhennan community in Jinfengshan Mountain,a field investigation was conducted. The intensity of human disturbance is divided into 3 levels: severe disturbance( close to the core scenic area within 40 m),medium disturbance( distant from the core scenic area at 40—80 m) and slight disturbance( far from the core scenic area at 80—120 m). The species richness index S,Shannon-Wienner index H,Simpson index D and Pielou index Jsware adopted to evaluate the level of species diversity in Phoebe zhennan community. The results showed that 155 species,belonging to 36 families and 136 genera were found in 9 plots with a total area of 3600 m2. The following results were also revealed in this investigation:( 1) the number of species decreased with the increase of disturbance intensity.( 2) In terms of the community structure,the diameter and height class were normally distributed with slight and medium disturbance,significant difference in community structure was observed among communities with three different disturbance intensities.Individuals under slight and medium disturbance were distributed in small and medium diameter class( 4 <DBH < 20 cm),and low and medium height class( 5<H<13 m). Individuals in severe disturbance were mainly distributed in small diameter class( DBH<8 cm) and big diameter class( DBH≥28 cm),and low height class( 3<H<7 m) and high height class( H≥15m).( 3) The species diversity indexes generally exhibited slight disturbance > medium disturbance > severe disturbance respectively. The richness index S,Shannon-Wienner index H and Pielou index Jswwere decreased with the increase of human disturbance intensity. This study suggests that human disturbance had negative effects on the diversity and stability of Phoebe zhennan community,which calls for urgent actions to solve the conflict between human disturbance and the protection of species diversity. 'Close to nature'forestry,a theory about sustainable forest management which integrates consideration of social,economic,and environmental factors in decision making is proposed to be taken into practice in this study area.