Institute of Landscape Ecology and Resource Management, Research Centre for Biosystems, Land Use and Nutrition (IFZ), Justus Liebig University, Giessen, Germany.
Institute of Ecology, Friedrich Schiller University, Jena, Germany.
PLoS One. 2018 Jul 6;13(7):e0200191. doi: 10.1371/journal.pone.0200191. eCollection 2018.
Most island-ecology studies focus on the properties of entire island communities, thus neglecting species-environment relationships operating at the habitat-level. Habitat-specific variation in the strength and sign of these relationships will conceal patterns observed on the island scale and may preclude a mechanistic interpretation of patterns and processes. Habitat-specific species-environment relationships may also depend on the descriptor of ecological communities. This paper presents a comprehensive plot-based analysis of local vegetation composition and species diversity (species richness and species evenness) of (i) rocky shore, (ii) semi-natural grassland and (iii) coniferous forest habitats in three Baltic archipelagos in Sweden. To identify differences and consistencies between habitats and descriptors, we assessed the relative contributions of the variable-sets "region", "topography", "soil morphology", "soil fertility", "soil water", "light availability", "distance" and "island configuration" on local vegetation composition, species richness and species evenness. We quantified the impact of "management history" on the descriptors of local grassland communities by a newly introduced grazing history index (GHI). Unlike species diversity, changes in vegetation composition were related to most of the variable-sets. The relative contributions of the variable-sets were mostly habitat-specific and strongly contingent on the descriptor involved. Within each habitat, richness and evenness were only partly affected by the same variable-sets, and if so, their relative contribution varied between diversity proxies. Across all habitats, soil variable-sets showed highly consistent effects on vegetation composition and species diversity and contributed most to the variance explained. GHI was a powerful predictor, explaining high proportions of variation in all three descriptors of grassland species communities. The proportion of unexplained variance was habitat-specific, possibly reflecting a community maturity gradient. Our results reveal that species richness alone is an incomplete representation of local species diversity. Finally, we stress the need of including habitat-based approaches when analyzing complex species-environment relationships on islands.
大多数岛屿生态学研究都集中在整个岛屿群落的特性上，因此忽略了在生境层面上运作的物种-环境关系。这些关系的强弱和符号在生境上的具体变化将掩盖在岛屿尺度上观察到的模式，并可能排除对模式和过程的机制解释。生境特异性的物种-环境关系也可能取决于生态群落的描述符。本文对瑞典三个波罗的海群岛的岩石海岸、半自然草地和针叶林栖息地的局部植被组成和物种多样性（物种丰富度和物种均匀度）进行了全面的基于斑块的分析。为了确定栖息地和描述符之间的差异和一致性，我们评估了变量集“区域”、“地形”、“土壤形态”、“土壤肥力”、“土壤水分”、“光照可用性”、“距离”和“岛屿配置”对局部植被组成、物种丰富度和物种均匀度的相对贡献。我们通过引入新的放牧历史指数（GHI）来量化“管理历史”对当地草地群落描述符的影响。与物种多样性不同，植被组成的变化与大多数变量集有关。变量集的相对贡献大多是生境特异性的，并强烈依赖于所涉及的描述符。在每个栖息地内，丰富度和均匀度仅部分受到相同变量集的影响，如果是这样，它们在不同多样性代理之间的相对贡献也会有所不同。在所有栖息地中，土壤变量集对植被组成和物种多样性具有高度一致的影响，并对解释的方差贡献最大。GHI 是一个强大的预测因子，可以解释草地物种群落的所有三个描述符的大部分变异。未解释方差的比例是生境特异性的，可能反映了群落成熟度梯度。我们的结果表明，仅物种丰富度是局部物种多样性的不完整表示。最后，我们强调在分析岛屿上复杂的物种-环境关系时需要包括基于生境的方法。
