Community assembly can change over time following variations in connectivity among habitats. Previous studies have demonstrated the influence of seasonal pulse floods on community structures by facilitating species dispersal, but the effects of short-term flash floods have been poorly investigated. We investigated fish community structures before and after a short-term flood in drainage ditches of paddy fields in the Kita River basin, Japan. The study sites were classified into three connectivity types, “Transient” (connected only during the flood, with a temporally disappearing vertical gap between drainage ditches and downstream rivers), “Connected” (always connected, without the vertical gap), and “Disconnected” (always not connected, with the vertical gap). The abundance of Misgurnus anguillicaudatus, the only species that dispersed from paddy fields to drainage ditches, increased after the flood irrespective of the connectivity types, although the total abundance of the other species significantly increased after the flood only in the “Transient” sites. The dissimilarity of species composition between the (n − 1)-th and n-th surveys at each site was consistently low in the “Connected” and “Disconnected” sites, whereas it rose just after the flood and gradually declined in the “Transient” sites. Species composition was significantly different among the connectivity types, indicating that some fish species need stable connectivity even during the non-flood period. The results showed that the short-term flood facilitated fish dispersal from paddy fields by the increased water discharge and that from downstream rivers by the temporary removal of vertical gap, emphasizing the importance of hydrological connectivity for biodiversity conservation in an agricultural landscape.

中文翻译：

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连通性和短期洪水交互影响农业景观稻田排水沟鱼类群落组成

随着栖息地之间连通性的变化，群落组装可能会随着时间的推移而发生变化。先前的研究已经证明了季节性脉冲洪水通过促进物种扩散对群落结构的影响，但对短期山洪的影响的研究却很少。我们对日本北川流域稻田排水沟在短期洪水前后的鱼类群落结构进行了调查。研究地点被分为三种连通类型：“瞬时”（仅在洪水期间连通，排水沟与下游河流之间的垂直间隙暂时消失）、“连通”（始终连通，没有垂直间隙）和“断开” ”（始终不连接，具有垂直间隙）。泥鳅是唯一从稻田扩散到排水沟的物种，无论连通性类型如何，洪水后其丰度均有所增加，尽管其他物种的总丰度在洪水后仅在“短暂”地点显着增加。在“连通”和“断开”站点中，每个站点的第 ( n  − 1) 次和第 n次调查之间的物种组成差异始终较低，而在洪水发生后不久，该值上升，并在“瞬态”站点中逐渐下降。 ”网站。连接类型之间的物种组成存在显着差异，这表明某些鱼类即使在非洪水时期也需要稳定的连接。结果表明，短期洪水通过增加排水量促进了鱼类从稻田的扩散，并通过暂时消除垂直间隙促进了下游河流的鱼类扩散，强调了水文连通性对于农业景观生物多样性保护的重要性。