The negative effects of habitat loss on biodiversity are undisputed, while the effect of habitat configuration, i.e., the spatial arrangement of habitat area, has been debated for decades. To develop a more comprehensive understanding, it is important to know when and how configuration matters. In this study, we tested whether forest configuration influences the richness of species in groups characterized by varying shade tolerance in different ways and how such effects are related to habitat amount (i.e., the percentage of forest cover) at the landscape scale. Based on 104 survey plots (each measuring 1 ​km) of vascular plants on the Swiss Plateau, and using two statistical approaches (i.e., multiple regression and path analysis), we modeled the effects of habitat amount and configuration (measured as number of forest patches, total edge length, and proximity index) across all the plots and separately for three habitat amount classes: <10%, 10%–30%, and >30% forest cover. When we modeled all plots together, we found that, after controlling for habitat amount, the forest configuration significantly affected species richness. When we considered the different habitat amount classes separately, most of the significant effects of habitat configuration on species richness occurred only for habitat amounts of <10% forest cover. Additionally, the response to forest configuration differed among species with different shade tolerances. When forest area was <10%, the effects of the number of patches and the total edge length on the species richness of light-demanding forest species were greater than the effect of habitat amount, whereas neither configuration metric affected the richness of shade-tolerant species. In conclusion, our findings highlight the importance of configuration in landscapes with a small amount of habitat. At the same time, they demonstrate that considering the confounding factors (e.g. species traits) is important for understanding the effects of forest configuration on biodiversity and that generalizations remain a challenge for landscape ecology.

中文翻译：

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瑞士高原森林覆盖梯度生境结构对生物多样性的影响


栖息地丧失对生物多样性的负面影响是无可争议的，而栖息地配置（即栖息地区域的空间布局）的影响几十年来一直存在争议。为了获得更全面的理解，了解配置何时以及如何发挥作用非常重要。在这项研究中，我们测试了森林配置是否会影响以不同方式改变耐荫性的群体的物种丰富度，以及这种影响如何与景观尺度上的栖息地数量（即森林覆盖百分比）相关。基于瑞士高原上 104 个维管植物调查样地（每个样地面积为 1 公里），并使用两种统计方法（即多元回归和通径分析），我们模拟了栖息地数量和配置（以森林数量来衡量）的影响。斑块、总边长和邻近指数）跨越所有地块，并分别针对三个栖息地数量类别：<10%、10%–30% 和 >30% 森林覆盖率。当我们对所有地块进行建模时，我们发现，在控制栖息地数量后，森林配置显着影响物种丰富度。当我们分别考虑不同的栖息地数量类别时，大多数栖息地配置对物种丰富度的显着影响仅发生在森林覆盖率<10%的栖息地数量上。此外，具有不同耐荫性的物种对森林配置的反应也不同。当森林面积<10%时，斑块数量和总边长对喜光森林物种丰富度的影响大于栖息地数量的影响，而这两种配置指标均不影响耐阴物种丰富度物种。 总之，我们的研究结果强调了少量栖息地景观配置的重要性。同时，他们证明，考虑混杂因素（例如物种特征）对于理解森林配置对生物多样性的影响非常重要，并且概括仍然是景观生态学的挑战。