Diversity and Community Stability of Understory Vegetation in the Pinus massoniana Forest after Transformation in Thousand-island Lake Area
[Objective]Transforming Pinus massoniana coniferous forest into broadleaved forest is benefi-cial to improving the structure and function of forest ecosystem and has significant influence on the regen-eration and succession of understory vegetation.The analysis of the diversity and community stability of understory vegetation after forest transformation can provide reference for sustainable forest management.[Method]In this study,based on the four types of stand transformation(i.e.,Ⅰtrees,Ⅲ clear cutting and promoting regeneration,clear cut-ting and Ⅳ clear cutting and planting broadleaf trees)of Pinus massoniana forests in Thousand-island Lake Forest area,Chun'an county,and control treatment(V no-transformation forest)),the species com-position,diversity and community stability of understory vegetation were investigated.The relationship between understory species composition and stand factors was analyzed,and the relationship between species diversity and community stability was also explored.[Result]The difference of understory domin-ant species among different stands was lower in shrub layer than in herb layer.The understory species di-versity in control group was significantly lower than that in transformed stand(P<0.05)and the species di-versity of herb layer in type Ⅳ was significantly higher than that in other types(P<0.05).The stand factors could explain about 40％of understory species variation and had higher effect on the species composition of herb layer than that of shrub layer.Among these,the canopy density was the most important factor.In the early stage of stand transformation,the understory community stability in mode Ⅴ was the best,fol-lowed by Ⅰ,Ⅱ,Ⅲ,and Ⅳ.The community stability of shrub layer had low correlation with species diversity,while the stability of herb layer was negatively correlated with species diversity(P<0.05).[Conclusion]In the early stage of broad-leaf transformation of P.massoniana forest in Thousand-island Lake area,the di-versity of herbaceous layer was significantly improved mainly by reducing canopy density,but the stability of understory vegetation community was low under clear cutting treatments.Therefore,considering veget-ation diversity and community stability,appropriate thinning and tending measures can promote the devel-opment of understory vegetation in P.massoniana forest.
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