千岛湖破碎化景观中灌木层植被的边缘效应

景观破碎化经常引起生态系统的边缘效应.千岛湖典型破碎化景观中岛屿灌木层植物的边缘效应,在10个孤立岛屿上选取灌木层植物物种作为研究对象,采用样方法调查其种类和数量.对野外调查的物种数据进行单因素方差分析,结果显示,F=23.386,P=0.000＜0.01,表明物种丰富度差异显著.用Shannon指数、Simpson指数和Pielou均匀度指数对两种环境中的植物种类多样性进行定性分析,在边缘样地,H=2.304、D=0.883、E=0.880;在内部样地,H=1.716、D:0.751、E=0.755.表明岛屿边缘的物种多样性在各个样地中都高于内部.而且岛屿边缘存在特有种,例如牡荆(Vitex negundo L.var.cannabi folia)和木莓(Rubus swinhoei Hcnce).物种相似性系数的变化范围较大(B=0.300,0.800]),表明植物种类对景观破碎化影响的反应比较缓慢,但这种反应在某些岛屿已经表现出来.进一步的Spearman相关性分析表明,岛屿面积和灌木层物种无论在边缘样地还是内部样地的相关性都不显著.

Edge effects of landscape fragmentation on the shrub-layer vegetation in the One-Thousand Island Lake

Landscape fragmentation often lead to edge effects on ecosystems.Edge effects of shrub-layer plants on islands in typical fragmental area of Thousand-island Lake were analyzed.On 10 less-disturbed and more isolated islands,shrub-layer plant species was selected as study object and composition and abundance of the shrub-layer species were recorded by quadrate method.The results of one-way variance analysis(ANOVA) showed that richness of species differed significantly((F=23.386,) P=0.000<0.01).Specifically,both plant abundance and species richness in edge environment were higher than those in interior environment.The plant species diversity for the two environments were quantified using Shannon-Wiener Index(H),Simpson Index(D),and Pielou Evenness Index(E).For the edge,H=2.304,D=0.883,and E=0.880;for the interior,H=1.716,D=0.751,and E=0.755.Clearly,plant species diversity was higher at the edge than the interior of the islands.Also,several species,such as Vitex negundo L.var.cannabifolia,and Rubus swinhoei Hance,were only found in the edge environment.The measure of species similarity between the edge and interior varied greatly(B=0.300,0.800]).This indicates that the plant species diversity of at least some of the islands has been significantly affected by landscape fragmentation.Further analysis using Spearman correlation showed that the shrub-layer plant species richness was not significantly correlated with island area in either the edge or interior environment.