Data from: The spatial scaling of saprotrophic fungal beta diversity in decomposing leaves

Assembly of fungal communities remains poorly understood in part because of the daunting range of spatial scales that may be involved in this process. Here, we use individual leaves as a natural sampling unit, comprising spatially distinct habitat and/or resource patches with unique histories and suites of resources. Spatial patterns in fungal beta diversity were tested for consistency with the metacommunity paradigms of species sorting and neutral dynamics. Thirty senesced leaves were collected from the forest floor (O horizon) in replicate upland forest, riparian forest and vernal pool habitats. We quantified spatial distance between leaves, and fungal community composition was assayed by terminal restriction fragment length polymorphism. Significant distance-decay relationships were detected at all but one upland site. This is the first study where changes in fungal community composition were quantified across discrete adjacent habitat patches, providing evidence that fungal distance decay is operational at a scale of centimetres. Although leaves of differing lignin contents were sampled from each site, leaf type was not consistently important in explaining variation in fungal community composition. However, depth of a leaf within the forest floor significantly influenced community composition at five of six sites. Environmental heterogeneity associated with depth could include moisture gradients, relative influence of soil or spore colonization, and impact of forest floor biotic community (i.e. collembola and earthworms). Because the influence of spatial distance and depth on fungal community composition could not be disentangled, both species-sorting and neutral processes may be embedded within the distance-decay relationships that we found.

真菌群落组装机制迄今仍未得到充分阐释，其部分原因在于该过程可能涉及的空间尺度范围极为宽泛，令相关研究难以全面覆盖。本研究以单片叶片作为天然采样单元，这些叶片对应空间上相互独立的生境或资源斑块，各自拥有独特的形成历史与资源组合。我们针对真菌β多样性（beta diversity）的空间分布格局，检验其是否契合物种分选与中性动态两类集合群落范式。我们从重复布设的高地森林、河岸森林与季节性池沼三类生境的森林地表（O层）中，采集了30片枯落叶。我们定量了叶片间的空间距离，并采用末端限制性片段长度多态性（terminal restriction fragment length polymorphism）分析法测定了真菌群落组成。除一处高地森林样地外，其余所有样地均检出显著的距离衰减关系。本研究首次对相互独立的邻接生境斑块间的真菌群落组成变化进行了定量分析，为真菌距离衰减现象在厘米尺度上切实发挥作用提供了实证依据。尽管我们从每个样地采集了木质素含量各异的叶片，但叶片类型在解释真菌群落组成变异时，并未表现出一致的显著性影响。然而在6个样地中的5个样地里，叶片在森林地表中的埋藏深度均对真菌群落组成产生了显著影响。与埋藏深度相关的环境异质性可涵盖湿度梯度、土壤或孢子定殖的相对影响，以及森林地表生物群落（即弹尾虫与蚯蚓）的作用。由于我们无法区分空间距离与埋藏深度对真菌群落组成的各自影响，因此本研究观测到的距离衰减关系中，可能同时蕴含了物种分选与中性动态两类过程。