Influence of Vegetation on Trench Formation in Temperate Salt marshes

de Groot, Lissie (2019) Influence of Vegetation on Trench Formation in Temperate Salt marshes. Master's Thesis / Essay, Ecology and Evolution.

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Abstract

Global salt marshes have declined over the last decades. Tidal channels form naturally in salt marshes and the processes of initiation and evolution are poorly understood. Research on natural hydrologic processes in relation to the presence of vegetation may be a key factor for channel development. The density and typical dominant vegetation species differ in salt marsh zones. This is thought to have different influences on the hydro geomorphology of salt marshes. This thesis is dedicated to understanding the interaction between vegetation (density and type) during the channel initiation and evolution. Therefore the research question is: how does vegetation type and density contribute to channel formation in salt marshes located in temperate zones? Recent publications showed that the initiation of channels was influenced by the presence of vegetation in high density patches with a significant diameter of larger than two meters. In contrast, smaller and more dispersed vegetation has little influence on tidal channels. Higher elevated regions contain slower processes in which the vegetation contributes to channel stabilization and geometric efficiency. Meanders may occur depending on the sedimentation and erosion rate that is altered by vegetation types which influences the depth-width ratio. The vegetated channels become deeper not necessary wider if vegetation occurs on the banks. The geometric efficiency reduces in non-vegetated areas. The dominant vegetation in the pioneer zone and low-mid elevated zone has different life traits. The fast colonizers with expansion trough seedlings showed to have a bank stabilizing function if the morphological processes are low. Slow colonizers that expand laterally are more likely to initiate channel formation since these will have higher clump densities. The root depth differed for all species that caused the geomorphology to change, since the grain size of sediments is altered. Growth strategies diverged for the dominant species with the first haplotypic colonizer to grow dispersed and the later dominant grasses to grow in higher density clumps. The grasses spartina growing through lateral expansion or by both lateral dispersed seeds and lateral expansion. Channel evolution networks should be studied as a whole in order to understand the environmental conditions. In addition, models that are explored are often simplifications of the reality of environmental conditions of the salt marsh and need to be compared with empirical data.

Item Type:	Thesis (Master's Thesis / Essay)
Supervisor name:	Heide, T. van der
Degree programme:	Ecology and Evolution
Thesis type:	Master's Thesis / Essay
Language:	English
Date Deposited:	15 Aug 2019
Last Modified:	19 Aug 2019 12:11
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/20673

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