Abstract The spatial distribution of arbuscular mycorrhizal (AM) fungal communities has been studied at many scales, from global to local, but few studies have explored variation within the root system of individual plants. Spatial variation within root systems might be expected partly due to differences in the physiology, morphology and anatomy of different roots, as well as due to spatial variation in the composition of inoculum in soil. Here, we assessed AM fungal community variability at various local scales: within individual plant root systems and among plants separated by distances of a few centimetres to up to several metres. To do so, we sampled roots from four plant species (two grasses and two forbs) growing in a grassland experiencing experimentally altered rainfall patterns in replicated field plots. We found that AM fungal communities were highly dissimilar both within the same individual and among different plants. Communities sampled within the same root system were as dissimilar as those sampled from adjacent neighbours, but less dissimilar from those sampled at larger distances. The degree of within root system variability was as high for each watering treatment but varied among plant species in a way that was dependent on root phosphorus content. Overall, our results show that community dissimilarity levels are high even within the root systems of individual plants, possibly due to localised community assembly processes (e.g., priority effects and interactions among AM fungal species), but that the degree of homogenisation within a root system is partly dependent on host plant attributes.

中文翻译：

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单个植物根系内丛枝菌根真菌群落的变异性很高，并受寄主物种和根磷的影响

摘要 丛枝菌根 (AM) 真菌群落的空间分布已经在从全球到局部的多个尺度上进行了研究，但很少有研究探讨单个植物根系内的变异。根系内的空间变化可能部分是由于不同根的生理、形态和解剖结构的差异，以及由于土壤中接种物组成的空间变化。在这里，我们评估了不同局部尺度的 AM 真菌群落变异性：在单个植物根系内和在距离几厘米到几米的植物之间。为此，我们对生长在草地上的四种植物物种（两种草和两种杂草）的根进行了采样，这些植物在重复的田间地块中经历了实验性改变的降雨模式。我们发现 AM 真菌群落在同一个体和不同植物之间高度不同。在同一根系统内采样的群落与从相邻邻居采样的群落一样不同，但与在较远距离采样的群落不太相似。每次浇水处理的根系内变异程度都很高，但植物物种之间的差异程度取决于根磷含量。总体而言，我们的结果表明，即使在单个植物的根系内，群落差异水平也很高，这可能是由于局部群落组装过程（例如，AM 真菌物种之间的优先效应和相互作用），但根系内的同质化程度部分取决于寄主植物属性。