Worldwide, stream water is increasingly loaded with sediments and nutrients, due to processes such as accelerated soil erosion and overfertilization caused by agricultural intensification. This leads to increases in eutrophication and silting up of bottom sediments. Floodplains can play an important role in mitigating these problems, by removing sediment from rivers via water filtration and retention. Fine sediment is accumulated on the soil in between plants as well as on plant surfaces. However, it is still poorly understood how plant species facilitate leaf surface sedimentation via their leaf traits. In a flume experiment, we investigated to what extent the leaf traits (area, length, perimeter, pinnation, pubescence, surface roughness, flexibility and wettability) influence leaf surface sedimentation. We exposed leaves of 30 plant species to an artificial flood, and measured the fine sediment load the leaves captured after 24 h. Our results show that leaf traits overall explain 65% of the variation of fine sedimentation on leaves. Especially adaxial pubescence and leaf area strongly drove sedimentation. Hairy leaves accumulate more sediment per leaf area, presumably, because hairs create a buffer zone of reduced flow velocity which enhances sedimentation between the hairs. Additionally, for leaves with no or few hairs, sedimentation decreased with increasing leaf area, because most likely the more turbulent boundary layer of larger leaves allows less sediment to settle. Our results provide a first understanding of how plants can be selected based on their leaf traits for maximizing the sediment retention on floodplains, thereby providing a key ecosystem service.

中文翻译：

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洪水期间，叶面积和柔毛会导致叶表面沉积。


在世界范围内，由于农业集约化造成的加速水土流失和过度施肥等过程，溪水中越来越多地含有沉积物和养分。这导致富营养化和底部沉积物淤积增加。洪泛区可以通过水过滤和滞留去除河流中的沉积物，在缓解这些问题方面发挥重要作用。细小的沉积物积聚在植物之间和植物表面的土壤上。然而，人们对植物物种如何通过其叶子特性促进叶面沉积仍知之甚少。在水槽实验中，我们研究了叶子特征（面积、长度、周长、羽状排列、柔毛、表面粗糙度、柔韧性和润湿性）对叶子表面沉降的影响程度。我们将 30 种植物的叶子暴露在人工洪水中，并测量了 24 小时后叶子捕获的细泥沙负荷。我们的结果表明，叶子性状总体解释了叶子上细沉降变化的 65%。尤其是正面的柔毛和叶面积强烈地驱动沉降。有毛的叶子在每个叶面积上积累了更多的沉积物，大概是因为毛产生了流速降低的缓冲区，从而增强了毛之间的沉降。此外，对于没有或很少有毛发的叶子，沉降随着叶面积的增加而减少，因为很可能较大叶子的更湍流边界层允许更少的沉积物沉降。我们的研究结果首次了解了如何根据叶子特征选择植物，以最大限度地提高洪泛区的沉积物滞留能力，从而提供关键的生态系统服务。