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.研究背景：生态位（ecological niche）与空间过程是塑造植物群落物种组成的核心驱动因素。然而，两类因子的相对重要性会随生境差异产生显著变化。 研究目的：为明确环境条件与多尺度空间过程对森林植被物种组成的影响，本研究选取兼具多样性的亚山地景观中的南向坡地，以起源于矮林作业的郁闭萌生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）方法，通过‘交错’矩阵探究嵌套空间尺度的效应；运用变异划分程序评估空间与环境组分的相对贡献；借助冗余分析（redundancy analysis）识别特定环境变量的影响。 研究结果：植被组成与环境变量（主要为持水能力与钙（Ca）含量）以及大尺度（约15 km）、中尺度（约3.5 km~1.0 km）下的空间过程（如扩散限制）显著相关；而在小尺度（<1 km）范围内，上述因子与物种组成并无关联。 研究结论：本研究涉及的森林植被可被视为一个集合群落（metacommunity），物种组成的主要驱动因子为物种分选与扩散限制。