林分密度对云顶山柏木人工林群落结构和物种多样性的影响

Effects of stand density on community structure and species diversity of Cupressus funebris plantation in Yunding Mountain, southwestern China

【目的】探索林分密度对柏木人工林群落结构和林下物种多样性及林下物种多样性与林分因子相关性的影响,为云顶山柏木人工林经营管理提供依据。【方法】以四川云顶山5种不同林分密度(A^E:500、650、800、950、1100株/hm^2)60年生柏木人工林为研究对象,采用典型样地法进行植被调查,综合分析其群落结构、物种组成和物种多样性指数(Pielou均匀度指数Jsw、Simpson优势度指数H′、Shannon-Wiener多样性指数H、和物种丰富度指数D)。【结果】(1)研究区内共记录植物170种,隶属于68科136属。不同密度下灌木层或草本层优势种多属阴性、耐阴性或适应性强的植物。(2)随着林分密度的减小,灌木层物种多样性指数均呈先增后减的单峰变化,基本在密度B达到最大,除D外均无显著差异(P>0.05);草本层D、H、H′则呈先增后减再增再减的双峰变化,在密度B和D出现峰值,不同密度间各指数差异性显著。林分密度和郁闭度与灌木层D呈极显著负相关,与草本层H、H′、Jsw呈显著或极显著正相关。(3)密度A群落径级和高度级结构均呈波动状不规则分布,其余密度下均呈单峰型分布。密度B群落内中、大乔木个体占比相对较多,不同大小个体数在群落中分布趋于合理,群落稳定性较好。【结论】650株/hm^2为云顶山柏木人工林的相对最适林分密度,利于维持群落结构稳定并提高林下物种多样性。

[Objective]The effects of stand density on the community structure and species diversity of Cupressus funebris plantation and the correlation between species diversity and stand factors were explored,providing a basis for the management of Cupressus funebris plantation in Yunding Mountains,southwestern China.[Method]The research objects were five different stand densities(A-E:500,650,800,950,1100 tree/ha)of 60 years Cupressus funebris in Yunding Mountain,Sichuan Province,southwestern China.The vegetation was investigated by typical plot method.The community structure,species composition and species diversity index(Pielou evenness index Jsw,Simpson dominance index H’,Shannon-Wiener diversity index H and species richness index D)were comprehensively analyzed.[Result](1)A total of 170 species of plants were recorded in the study area,belonging to 136 genera and 68 families.The dominant species in shrub layer or herb layer under different densities were mostly shady,shade-tolerant or adaptable plants.(2)With the decrease of stand density,the trend of species diversity index in shrub layer increased first and then decreased.It reached the maximum at density B,with no significant difference except D(P>0.05).The trend of D,H and H’in herbaceous layer increased first,then decreased,then increased and then decreased.The peak values appeared in density B and D,and there were significant differences among different densities.Stand density and canopy density were negatively correlated with shrub layer D,and significantly positively correlated with herb layer H,H’and Jsw.(3)Distribution between diameter and height structure of density A community was irregular and fluctuated,while distribution of other densities was unimodal.In density B community,medium and large individual trees accounted for a relatively large proportion of individuals,and the stability of the community was better.[Conclusion]The relative optimum stand density of cypress plantation in Yunding Mountain is 650 tree/ha,which is very helpful to maintain the stability of community structure and improve the species diversity under the forest.