北京东灵山暖温带落叶阔叶林地形和林分结构对林下草本植物物种多样性的影响

Effects of topography and stand structure of warm temperate deciduous broad-leaved forest on understory herb diversity in Donglingshan,Beijing

森林群落林下草本植物物种多样性丰富,然而大多数森林物种多样性研究集中在乔木层,对林下草本植物物种多样性及其影响因子的研究较少。本研究基于北京东灵山20 ha森林动态监测样地450个1 m×1 m的草本样方调查数据,选择物种丰富度指数(R)、Shannon-Wiener多样性指数(H′)、Simpson优势度指数(D)和Pielou均匀度指数(E)作为草本植物物种多样性数据指标,分析了林下草本植物物种多样性与地形和林分结构的相关关系;并采用Pearson相关性分析、回归分析、冗余分析(RDA)及层次分割的方法,探讨了地形因子和林分因子对草本植物物种多样性的影响。结果表明:(1)林下草本植物的Shannon-Wiener多样性指数与坡向呈显著负相关(P<0.05),随坡向增大(由阳坡转向阴坡)而呈下降趋势;4个多样性指数与海拔、坡度和凹凸度均无显著相关性。(2)物种丰富度指数和Shannon-Wiener多样性指数随林分密度和林地物种丰富度的增大呈下降的趋势,但随平均胸径的增大呈上升的趋势;各物种多样性指数均与胸径变异系数无显著相关性。(3)层次分割结果表明,环境因子对林下草本植物物种多样性的解释率为:林分密度>平均胸径>胸径变异系数>海拔;林分密度是影响林下草本植物物种多样性的主要因子。本研究揭示了不同地形、林分结构对暖温带落叶阔叶林林下草本植物物种多样性的影响,以期加强对森林生物多样性的全面认识,促进森林生态系统及生物多样性的保护。

Aim:Topographic and stand structure are important factors affecting species diversity of understory communities.Our objective was to explore the effects of different topographic factors and forest stand structure on the species diversity of herbaceous plants in a warm temperate deciduous broad-leaved forest.Methods:Based on the survey data of 4501 m×1 m herbaceous plots in the 20 ha Donglingshan forest dynamics plot,Beijing,we used species richness index,Shannon-Wiener diversity index,Simpson dominance index and Pielou evenness index as the indicators of herbaceous species diversity to analyze the changes of each diversity index with different factors of topographic and forest stand structure.Meanwhile,we utilized Pearson correlation analysis,regression analysis,redundancy analysis(RDA),and hierarchical partitioning methods to explore the influence of topographic and forest stand structure factors on herbaceous species diversity.Results:(1)The herbaceous Shannon-Wiener diversity index in the forest was negatively correlated with the slope aspect(P<0.05),and the Shannon-Wiener diversity index decreased with the slope aspect(from sunny to shady slopes).The four diversity indices had no significant correlation with elevation,slope,and concavity.(2)The species richness index and Shannon-Wiener diversity index decreased with the increase in stand density and forest species richness but increased with the rise of mean DBH.The four species diversity indices were not significantly correlated with coefficient of variation of DBH(DBHcv).(3)The hierarchical partitioning method showed that environmental factors explained herbaceous species diversity as follows:stand density>DBH>DBHcv>elevation.Stand density was the main factor affecting the species diversity of herbaceous plants under the forest.Conclusion:This study revealed the effects of different topographic factors and forest stand structure factors on the diversity of herbaceous plants in the warm temperate deciduous broad-leaved forest,and confirmed that stand density was the key factor.Our findings will contribute to the comprehensive understanding of forest biodiversity in the promotion and protection of forest ecosystem and biodiversity.