Sediment and nutrient retention are important ecosystem functions floodplain meadows fulfil. While it is known that the inundated floodplain vegetation purifies the water during floods, little is known about the processes behind. I investigated the effect of the vegetation structure on sedimentation at three hierarchical scales, leaf, patch, and floodplain scale and used two approaches, experiments and an in situ field study.
In the leaf experiment (study 1) I inundated single leaves into sediment rich water. The results showed that leaf pubescence increased sedimentation on leaf surfaces and that for leaves without hairs, the sedimentation increased with decreasing leaf area.
In the flume experiment (study 2) I investigated the effects of community characteristics of vegetation patches regarding their capacity to capture sediment. I manipulated the leaf pubescence, the community density, the community height and the structural diversity (high-high vs high-low growing species) of the patches. The results show that all four investigated community characteristics increased the sediment retention.
In the second flume experiment (study 3), I investigated the effect of species richness of vegetation patches on sediment retention. The results showed the importance of the vegetation biomass and identity effects of single species, but no clear effect of species richness.
For the in situ field measurements (study 4), I measured sedimentation during a real flood event along the Mulde River in Germany. With sediment traps and biomass harvests I quantified the sedimentation underneath as well as on the vegetation. The results showed that besides the vegetation biomass, the topographical parameter ‘hydrological distance’ (pathway of lowest elevation the water travels to the site) is important for sediment and especially nutrient retention. Even though sediment retention is highest close by the river, sedimentation is still reasonably high far insight the floodplain and especially nutrient retention (C, N and P) increase with hydrological distance.
From the sum of results I can derive four management strategies for floodplains to increase the sediment retention. First, reduced mowing for more standing biomass during flood season, wherefore trade-offs with other ecosystem functions need to be evaluated carefully. Second, promotion of structural diversity, possible via species diversity. Third, promotion of species with characteristics that increase sediment, such as pubescent leaves. Forth, preserving or recreating topographic complexity in the floodplain. Overall, I showed that the specific structures of herbaceous vegetation are highly beneficial for sediment and nutrient retention on floodplains.:Table of contents
1. General introduction 6
1.1 The Mulde River and the “Wilde Mulde” project 7
1.2 Sediment retention on floodplains 8
1.3 Vegetation causes fine sedimentation 11
1.4 Structural characteristics 12
1.4.1 Structural identity of species 13
1.4.2 Structural identity of communities 14
1.4.3 Structural diversity of communities 15
1.5 Links between studies 17
2. Methodological features 19
2.1 Study area “Wilde Mulde” 19
2.2 Leaf roughness measurement 22
2.3 Experimental set up of the flume experiment 24
3. Original contributions 26
3.1 Paper 1 - Leaf area and pubescence drive sedimentation on leaves surfaces during flooding 26
3.2 Paper 2 – Plant structural diversity alters sediment retention on and underneath herbaceous vegetation in a flume experiment 44
3.3 Paper 3 – Effects of plant species identity overrides diversity effects in explaining sedimentation within vegetation in a flume experiment 65
3.4 Paper 4 – Vegetation characteristics control sediment and nutrient retention on but not underneath vegetation in floodplain meadows 77
4. Discussion 107
4.1 Mechanistic parallels among scales 109
4.2 Effects of species diversity in relation to species identity 112
4.3 Transferability and its limitations 113
4.4 The ecosystem function of sediment retention 114
4.4.1 Floodplain management for sediment retention 115
4.4.2 Sediment retention in the context of other ecosystem functions 117
4.4.3 Floodplain management for sediment retention along the Lower Mulde River 119
5. Outlook 122
5.1 Leaf roughness 122
5.2 Diversity experiment 123
5.3 Approaches for new management strategies 124
5.4 Extrapolation with remote sensing 125
5.5 Sediment budget 126
6. Conclusion 128
7. References 130
8. Summary 143
9. Zusammenfassung 149
Acknowledgements 155
Author contribution statement 156
Curriculum vitae 164
List of publications 166
Selbstständigkeitserklärung 169
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:77552 |
| Date | 25 January 2022 |
| Creators | Kretz, Lena |
| Contributors | Universität Leipzig |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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