漓江河岸带枫杨群落主要木本植物种间联结与相关分析

Interspecific associations and correlations among the main woody plants in a Pterocarya stenoptera community in a riparian zone of Lijiang River,Guilin,Southwest China

种间联结能够反映植物群落中物种间的关系和群落的稳定程度,对植被的恢复与重建、生物多样性保护等具有重要的意义和价值。为了解漓江河岸带枫杨群落的种间联结特征,基于2×2联列表,通过方差比率(VR)、χ~2检验、Pearson相关系数、Spearman秩相关系数检验及PCA排序等,对枫杨群落主要木本植物种间关联性进行定量分析和生态种组划分。结果表明:(1)乔木层、灌木层以及乔木和灌木层的总体种间关联性均呈不显著正联结,表明枫杨群落处于较稳定的阶段;(2)χ~2检验结果显示,绝大多数种对呈不显著关联,说明群落各种对间关联较弱,各物种间呈独立分布格局;(3)Pearson相关检验和Spearman秩相关检验发现各层次的显著率均较低,种间相关性不显著的种对占绝大部分,种间相关性不强;(4)χ~2检验、Pearson相关系数检验和Spearman秩相关系数检验结果虽具有一致性,但也存在一定的差异,Spearman秩相关系数检验更具灵敏性,结合3种方法使用效果更佳;(5)根据PCA排序和种间联结关系,将20个主要物种划分为4个生态种组。

Interspecific plant associations, which are significant quantitative and structural characteristics, reflect relationships among species in a plant community as well as community stability, and they have important theoretical significance and application values for the restoration and reconstruction of vegetation, protection of biodiversity, and sustainable utilization of the plant community. For understanding the mechanisms underlying the formation of interspecific associations in Pterocarya stenoptera communities, the interspecific associations of the main woody plants in a riparian Pterocarya stenoptera community near Lijiang River were examined. A total of 20 sample plots were set up and investigated in the studied area. We selected 8 tree-layer species and 18 shrub-layer species on the basis of importance values, and quantitatively researched interspecific associations and correlations by using a set of methods, namely, variance ratio analysis of the overall association, X2 test, Pearson＇s correlation coefficient test, Spearman＇s rank correlation coefficient test, and principal component analysis （PCA） based on 2 × 2 contingency tables of species presence/absence and abundance per quadrat data. The results showed that the overall interspecific associations were non-significant, positive correlations among the main plant populations in the tree layer, shrub layer, and combined tree and shrub layer, and this reflected that the Pterocarya stenoptera community in the riparian zone of the Lijiang River is at a relatively stable developmental stage. The results of the X2 test showed that a vast majority of the species pairs were not significantly associated, reflecting a weak association among the various species pairs in the tree layer and shrub layer; most of the species showed an independent distribution pattern. Pearson＇s correlation coefficient and Spearman＇s rank correlation tests showed that the significance rates of the species pairs in the tree layer, shrub layer, and combined tree and shrub layer were lower, and the species pairs with insignificant interspecies correlations accounted for the majority of the species pairs in the tree layer, shrub layer, and combined tree and shrub layer. The results of theX2 test, Pearson＇s correlation coefficient test, and Spearman＇s rank correlation coefficient test were consistent; however, Spearman＇s correlation coefficient test was more sensitive than the X2 test and Pearson＇s correlation coefficient test, and could make up for the limitations of the X2 test and Pearson＇s correlation coefficient test. Therefore, it is better to investigate the interspecific association and correlation by combining the X2 test with Pearson＇s correlation coefficient and Spearman＇s rank correlation coefficient tests, because this approach can more accurately and reliably reveal the intrinsic relationship of interspecific associations and correlations among the plant species. According to the PCA and evaluation of interspecific relationships, the 20 main species in the tree and shrub layer were divided into four ecological species groups.