Nitrate pollution in aquatic ecosystems is still a major problem in Germany. Although the dynamics of various nitrate-related processes in floodplains remain partially unclear, there is a great potential to permanently remove nitrate from aquatic systems through denitrification as a relevant ecosystem function. However, the controlling factors and the dimension of the denitrification potential are still not fully understood due to the high complexity of the process, various possible explanatory variables, and the high spatial and temporal heterogeneity in floodplains. This study presents the combined assessment of potential soil denitrification rates, physical and chemical soil parameters, and hydrological parameters from six floodplains of four large German rivers, namely the Rhine, the Elbe, the Weser, and the Main. Based on multivariate statistics, results show that the denitrification potential of soil was largely unaffected by hydrology but almost solely controlled by soil pH. We hypothesized that these estimates could be further specified by incorporating the duration of average inundation, as this accounts for water saturation and nutrient supply - the major controlling variables for denitrification. Results provide evidence that the denitrification potential can only be fully exploited in frequently inundated floodplains. Thus, despite favorable soil conditions for denitrification, floodplains that have suffered from anthropogenic impacts lose their importance in nitrate removal for the river system. We conclude that pH and lateral hydrological connectivity are likely to be key factors that should be considered when estimating denitrification as an ecosystem function.

中文翻译：

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土壤特征和水文形态模式控制漫滩尺度的反硝化作用

水生生态系统中的硝酸盐污染仍然是德国的一个主要问题。尽管漫滩中各种硝酸盐相关过程的动态仍部分不清楚，但通过反硝化作为相关生态系统功能从水生系统中永久去除硝酸盐具有巨大潜力。然而，由于反硝化过程的高度复杂性、各种可能的解释变量以及泛滥平原的高度时空异质性，控制因素和反硝化潜力的维度仍不完全清楚。本研究对德国四大河流（即莱茵河、易北河、威悉河和美因河）的六个洪泛区的潜在土壤反硝化率、土壤物理和化学参数以及水文参数进行了综合评估。基于多元统计，结果表明土壤的反硝化潜力在很大程度上不受水文影响，而几乎完全受土壤pH值控制。我们假设可以通过纳入平均淹没持续时间来进一步指定这些估计值，因为这说明了水饱和度和养分供应 - 反硝化的主要控制变量。结果提供的证据表明，只有在经常被淹没的洪泛区才能充分利用反硝化潜力。因此，尽管有利于反硝化的土壤条件，但遭受人为影响的洪泛区在去除河流系统中的硝酸盐方面失去了重要性。