云南鸡足山半湿润常绿阔叶林群落木本植物多样性格局与环境解释

Spatial variation and determinants of woody plant species diversity in a semi-humid evergreen broad-leaved forest in the Jizu Mountains,Yunnan

生物多样性格局是生物群落构建过程的反映,有助于理解生态系统的物种共存机制。半湿润常绿阔叶林是亚热带西部半湿润气候下的地带性植被类型,对其群落内物种多样性的空间异质格局及影响因子的认识还比较缺乏,基于大样地的研究还未见报道。本文基于鸡足山20.16 ha森林动态监测样地504个样方的木本植物调查数据和TWINSPAN群落分类结果,分析了样方尺度上α多样性和β多样性的空间分布格局及其环境影响因子。结果表明:(1)样地内云南松(Pinus yunnanensis)群落及其乔木和灌木的物种丰富度均高于高山栲(Castanopsisdelavayi)群落和元江栲(C.orthacantha)群落;高山栲群落及其灌木物种丰富度低于元江栲群落,乔木物种丰富度则高于元江栲群落。相反,元江栲群落的Shannon-Wiener多样性指数最高,其次为高山栲群落,云南松群落的最低。基于净种间亲缘关系指数,元江栲群落、高山栲群落、云南松群落的谱系结构分别为聚集、随机、发散。(2)对物种丰富度存在普遍性影响的因子有土壤总氮、pH值、相对海拔高度、木本植物的胸高断面积之和;导致乔木种丰富度变化的主要因子有土壤总氮、pH值、胸高断面积之和;导致灌木种丰富度变化的主要因子是相对海拔高度、土壤总氮、坡度和地形湿度指数。(3)物种β多样性格局显示,随着空间距离和环境距离的增大,物种差异性和物种周转率增大,即环境越相似,群落越相似。上述结果表明,鸡足山样地中先锋性的云南松群落与稳定的元江栲群落和高山栲群落在物种多样性和构成上存在显著差异,指示了半湿润常绿阔叶林异质斑块所对应的物种共存和物种多样性维持特征,为进一步的机理性研究提供了有效证据。

Aims:Spatial patterns of biodiversity can reflect the community assembly processes and the mechanisms of species coexistence within ecosystems.The semi-humid evergreen broad-leaved forest is a type of vegetation zone located in the semi-humid climate of the western subtropical region of China.To date,there have been many studies investigating the species diversity of this type of vegetation,but studies into the patterns of spatial heterogeneity of species diversity and its determinants are still relatively lacking,and research utilizing large dynamics plot has not yet been reported.To better understand the maintenance mechanism of species diversity,we explored the characteristics of spatial heterogeneity and species diversity and their main environmental determinants in a 20.16 ha forest dynamics plot located in the Jizu Mountains.Methods:Based on data collected from woody plants and TWINSPAN classification results from 504 quadrats 20 m × 20 m in the 20.16 ha forest dynamics plot in the Jizu Mountains,this article utilized regression analysis and the Mantel test to analyze the distribution patterns of α and β diversity,and their correlation with respective environmental factors.Results:(1) In the plot,we found that the species richness of the Pinus yunnanensis community and its trees and shrubs were all higher than that of the Castanopsis delavayi community and C.orthacantha community;the C.delavayi community and its shrubs species richness were both higher than that of the C.orthacantha community,while its tree species richness was higher than C.orthacantha community.On the contrary,the Shannon-Wiener value of the C.orthacantha community was found to be the highest among all species,followed by the C.delavayi community,while the value of the P.yunnanensis community was the lowest.Based on the net interspecific relationship index(NRI),the phylogenetic structures of the C.orthacantha community,C.delavayi community,and P.yunnanensis community were clustering,random,and overdispersion,respectively.(2) The factors that demonstrated a universal impact on species richness included the total nitrogen and pH,the relative altitude,and the sum of basal area of woody plants.The main factors affecting the richness of tree diversity included total nitrogen level and pH and the sum of basal area.The dominant factor influencing shrub species richness was the relative altitude,followed by total nitrogen,slope,and the topographic wetness index.(3) The species β diversity pattern showed that differences in species composition and turnover rate increased with increasing spatial and environmental distances,indicating that the more similar the environment,the more similar the community.Conclusion:This study reflects the significant differences in species diversity and composition between the pioneer P.yunnanensis community and the stable C.orthacantha community and C.delavayi community in the Jizu Mountains forest dynamics plot,which describes the characteristics of species coexistence and species diversity maintenance corresponding to the heterogeneous patches of semi-humid evergreen broad-leaved forests,and provides a basis for further mechanistic investigations.