The effect of ecological niche and spatial pattern on the diversity of oak forest vegetation

Background: Ecological niche and spatial processes are known to shape the species composition of plant communities. However, the relative importance of these factors can vary considerably from one habitat to another.Aims: To determine the effect of environmental conditions and spatial processes on multiple scales on the species composition of forest vegetation, we studied a patchy system consisting of overgrown oak stands of coppice origin on slopes with a southern exposure in a diverse, submontane landscape.Methods: Spatial patterns were surveyed with the principal coordinate analysis of neighbour matrices method, using a ‘staggered’ matrix to examine the effect of nested spatial scales. The variation partitioning procedure was applied to assess the relative influence of spatial and environmental components. Redundancy analysis was carried out to detect the effect of particular environmental variables.Results: Vegetation composition was related to environmental variables (mostly water-holding capacity and Ca content), as well as spatial processes, such as dispersal limitation, at the large (ca. 15 km) and medium (ca. 3.5 km–1.0 km) scales, whereas at small scales (<1 km), these factors were not related to species composition.Conclusions: The vegetation of the studied forests should be considered as a metacommunity, and the main drivers of species composition are species sorting and dispersal limitation.

背景：生态位（Ecological niche）与空间过程共同塑造植物群落的物种组成，然而二者的相对重要性会因生境不同而存在显著差异。
研究目的：为探明环境条件与多尺度空间过程对森林植被物种组成的影响，我们以一处多样的亚山地景观中、南向坡地上起源于矮林作业的郁闭栎林斑块系统为研究对象。
研究方法：本研究采用邻域矩阵主坐标分析（principal coordinate analysis of neighbour matrices）法开展空间格局调查，并通过“交错矩阵（staggered matrix）”检验嵌套式空间尺度的效应；运用变异分割（variation partitioning）程序评估空间与环境组分的相对影响；借助冗余分析（redundancy analysis）识别特定环境变量的作用。
研究结果：在大尺度（约15 km）与中尺度（约3.5 km~1.0 km）下，植被组成与环境变量（主要为持水能力与钙含量）以及扩散限制（dispersal limitation）等空间过程相关；而在小尺度（<1 km）下，上述因子与物种组成无显著关联。
研究结论：本研究涉及的森林植被可被视为集合群落（metacommunity），物种组成的主要驱动因子为物种分选（species sorting）与扩散限制。