鄱阳湖草洲景观连通性对植物多样性的影响

Effects of grassland connectivity on plant diversity in Poyang Lake

在全球景观破碎化不断加剧的背景下,剖析景观连通度对生物多样性的影响机制对恢复生态过程和保护生物多样性具有深远意义。本文以鄱阳湖草洲为研究对象,综合考虑水位变化与物种扩散生态过程,在识别不同水位梯度下草洲分布格局的基础上,通过景观格局指数和基于图论的景观连通度指数相结合的方法,分析不同水位草洲景观结构连通度和功能连通度的动态变化,揭示草洲景观连通度对植物多样性的影响及其尺度效应,比较结构连通度与功能连通度对植物多样性格局的相对解释力。研究结果表明:①鄱阳湖草洲呈现“水落滩出、水进草退”的景观格局特征,随着水位的增加,草洲同时面临水体的淹没效应和分割效应,面积萎缩和破碎化并存;②随着水位的增加,草洲斑块面积不断减小、形状趋于简单、密度降低、破碎化加剧,景观结构连通度下降,难以连接的独立组分增加、斑块连通的可能性降低,景观功能连通度下降;③草洲景观连通度越高,景观尺度上的植物物种丰富度越高,斑块尺度上的植物群落相似性越大,功能连通度比结构连通度更加能解释植物多样性格局。本文研究结果可从景观连通度的新视角为湖泊地区景观格局优化和植物多样性保护提供参考。

With the acceleration of global landscape fragmentation,it is of great significance to reveal the impacts of landscape connectivity on biodiversity in order to restore ecological process and protect biodiversity.Taking the grassland of Poyang Lake as research object and from the integrated perspective of combined water level change and species dispersal,this study firstly analyzed the dynamics of grassland structural and functional connectivity respectively after identifying the distribution pattern of grassland at different water levels using landscape pattern indices and the graph-based connectivity indices.Then,the effects of grassland connectivity on plant diversity and the scale effects were discovered by means of the linear regression model.Moreover,the multiple stepwise linear regression model was applied to compare the relative explanatory power of structural and functional connectivity to plant diversity pattern.The results are shown as follows:(1)The grassland in Poyang Lake exhibits a landscape characteristic of"expanding when water falls while shrinking when water rises".It faces both inundation and segmentation effects of water with water level change,and its shrinkage always coexists with landscape fragmentation.(2)With the increase of water level,the area of grassland patch continues to shrink,the shape tends to be simple,the density reduces,and the fragmentation intensifies,resulting in a decrease of grassland structural connectivity.Meanwhile,the number of components increases,the probability of connectivity reduces,so that grassland functional connectivity decreases significantly.(3)The higher the connectivity of grassland,the higher the richness of plant species at the landscape scale,and the higher the similarity of plant communities at the patch scale.Functional connectivity is more effective in explaining plant diversity pattern than structural connectivity does.This study can provide some references for landscape pattern optimization and plant diversity conservation in lake areas from a new perspective of landscape connectivity.