Context Dead wood is a key habitat for saproxylic species, which are often used as indicators of habitat quality in forests. Understanding how the amount and spatial distribution of dead wood in the landscape affects saproxylic communities is therefore important for maintaining high forest biodiversity. Objectives We investigated effects of the amount and isolation of dead wood on the alpha and beta diversity of four saproxylic species groups, with a focus on how the spatial scale influences results. Methods We inventoried saproxylic beetles, wood-inhabiting fungi, and epixylic bryophytes and lichens on 62 plots in the Sihlwald forest reserve in Switzerland. We used GLMs to relate plot-level species richness to dead wood amount and isolation on spatial scales of 20–200 m radius. Further, we used GDMs to determine how dead wood amount and isolation affected beta diversity. Results A larger amount of dead wood increased beetle richness on all spatial scales, while isolation had no effect. For fungi, bryophytes and lichens this was only true on small spatial scales. On larger scales of our study, dead wood amount had no effect, while greater isolation decreased species richness. Further, we found no strong consistent patterns explaining beta diversity. Conclusions Our multi-taxon study shows that habitat amount and isolation can strongly differ in the spatial scale on which they influence local species richness. To generally support the species richness of different saproxylic groups, dead wood must primarily be available in large amounts but should also be evenly distributed because negative effects of isolation already showed at scales under 100 m.

中文翻译：

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腐木树种与山毛榉林中空间尺度上死木的数量和隔离有关

背景 枯木是腐木树种的主要栖息地，通常用作森林栖息地质量的指标。因此，了解景观中死木的数量和空间分布如何影响腐木群落对于维持高森林生物多样性非常重要。目标我们调查了死木的数量和隔离对四个腐木物种组的 alpha 和 beta 多样性的影响，重点是空间尺度如何影响结果。方法 我们在瑞士 Sihlwald 森林保护区的 62 个地块上清查了腐生甲虫、木栖真菌、外生苔藓植物和地衣。我们使用 GLM 将样地级别的物种丰富度与死木数量和 20-200 m 半径空间尺度上的隔离联系起来。更多，我们使用 GDM 来确定死木数量和隔离如何影响 Beta 多样性。结果大量死木增加了所有空间尺度上的甲虫丰富度，而隔离没有影响。对于真菌、苔藓植物和地衣，这仅适用于小空间尺度。在我们研究的更大范围内，死木数量没有影响，而更大的隔离降低了物种丰富度。此外，我们没有发现解释 beta 多样性的强一致模式。结论我们的多分类单元研究表明，栖息地数量和隔离在影响当地物种丰富度的空间尺度上可能存在很大差异。为了普遍支持不同腐氧基的物种丰富度，