Abstract
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.
Highlights
Worldwide, sediment and nutrient loads in stream water are increasing due to anthropogenic activities (Sharma and Rai 2004; Quilbé et al 2006; Hunter and Walton 2008; Jones et al 2012)
Our analysis of entire leaves showed that traits related to total area and pubescence on the upper side were the strongest predictors of sedimentation on the whole leaf surface
Sedimentation on the leaf surface decreased with total leaf area, but only on leaves with a low hair density (< 1 hair mm−2, p < 0.01, Fig. 2)
Summary
Sediment and nutrient loads in stream water are increasing due to anthropogenic activities (Sharma and Rai 2004; Quilbé et al 2006; Hunter and Walton 2008; Jones et al 2012). Floods counteract these processes by depositing sediment particles and nutrients from streams into floodplains, which function as a sink for both (Naiman and Décamps 1997; Asselman et al 2003; Walling et al 2003; Taylor et al 2008; Bouwman et al 2013). Oecologia (2020) 193:535–545 floodplains provide key ecosystem services of sediment and nutrient retention and water filtration (Hopkins et al 2018; Conte et al 2011). We need to improve our understanding of how plant and vegetation characteristics enhance sedimentation
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