Assembly processes shaping ecological communities can vary over time following variations of environmental conditions at different scales. Such temporal dynamism is exacerbated by climate change and increasing extreme events, and recent evidence suggests that, in turn, community composition and functions can vary substantially. However, empirical relationships between the spatio‐temporal dynamics of communities and that extreme events altering ecosystems are poorly investigated. We quantified the temporal dynamics of stream invertebrate communities over two years across 11 river basins prone to drying, covering a large geographical area of France. We tested predictions on the influence of the spatial arrangement and temporal dynamics of drying events across river networks. Combining a high temporal resolution of community description from taxonomic and functional perspectives, we quantified beta diversity over time and space and partitioned them into additive components: replacement of taxa and richness difference. Frequency and duration of drying events were precisely quantified and basins were classified based on the location of the drying events. We found a strong influence of the spatial drying pattern on the dissimilarities of community composition between sites. The high temporal variability of community structure was directly related to the frequency and duration of drying events. This temporal dynamism of communities was also strongly affected by the spatial drying pattern, indicating that fragmentation had a stronger effect on recolonisation processes for upstream‐drying basins. Finally, biological traits were unevenly distributed in space and time, suggesting a lack of functional redundancy that could have strong implications for ecosystem functions and services. The high temporal dynamics of communities highlighted in this study challenge the current definition of reference conditions in intermittent rivers, and the community sensitivity to frequency and duration of drying suggest that climate change might lead community dynamics to be increasingly driven by stochastic environmental variability.

中文翻译：

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干燥决定了河流无脊椎动物结构和功能β多样性的时间动态

形成生态群落的组装过程会随着环境条件的不同规模而随时间变化。气候变化和极端事件的增多加剧了这种暂时的活力，最近的证据表明，反过来，社区的组成和功能也可能发生很大变化。但是，关于社区的时空动态与改变生态系统的极端事件之间的经验关系研究很少。我们量化了11个易于干旱的流域（覆盖法国大面积地理区域）两年内河流无脊椎动物群落的时间动态。我们测试了跨河网的干旱事件的空间排列和时间动态影响的预测。从分类学和功能的角度出发，结合社区描述的高时间分辨率，我们量化了随时间和空间的beta多样性，并将其划分为附加成分：分类单元的替换和丰富度差异。精确地确定了干燥事件的频率和持续时间，并根据干燥事件的位置对盆地进行了分类。我们发现空间干燥模式对站点之间社区组成的不同有很大影响。群落结构的高时间变异性与干燥事件的频率和持续时间直接相关。社区的这种动态变化也受到空间干燥模式的强烈影响，表明破碎化对上游干燥盆地的重新定殖过程具有更强的影响。最后，生物学特征在时空上分布不均，表明缺乏功能冗余，可能会对生态系统功能和服务产生重大影响。这项研究中所强调的社区的高时空动态挑战了当前断断续续的河流参考条件的定义，并且社区对干旱频率和持续时间的敏感性表明，气候变化可能导致社区动态越来越受到随机环境变化的驱动。