University of Twente Student Theses
Modelling interspecific competition between the Salicornia and Spartina species and its effect on the bio-geomorphological development of salt marshes
Bandhoe, S. (2020) Modelling interspecific competition between the Salicornia and Spartina species and its effect on the bio-geomorphological development of salt marshes.
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| Abstract: | Salt marshes are known for their contribution to coastal protection, their ecological importance and their sediment trapping ability. Under the right circumstances, salt marshes can keep up with sea-level rise, which makes them a good addition to conventional coastal protection. Several studies have concluded that physical forces and the interspecific competition between salt marsh vegetation species in uence the development of salt marsh vegetation. Furthermore, it is known that vegetation development and colonisation behaviour in uences the bio-geomorphological development of salt marshes. Still, it is unknown how interspecific competition works and how it in uences the bio-geomorphological development of salt marshes. Therefore, this study aims to examine the in uence of the interspecific competition between two salt marsh vegetation species (the Salicornia europaea and the Spartina angilica) on the bio-geomorphological development of salt marshes. In this research, the interspecific competition between the Salicornia species and the Spartina species is schematised with the Lotka-Volterra competition framework, which is included in the vegetation module. This framework determines the growth of a salt marsh species depending on its vegetation density, the vegetation density of the competing species and the competition parameter. For the bio-geomorphological development of a multi-species salt marsh, three types of competition are tested: The development of a salt marsh without competition, with equal competition and with spatial competition. The actual simulations of 10 years of the bio-geomorphological development of salt marshes are preformed by including the Lotka-Volterra competition framework in the vegetation module in Python. This vegetation module is coupled to Delft3D Flexible Mesh (DFM), which is a numerical model that determines the hydrodynamics and the morphodynamics based on the vegetation development. From the different model simulations, it is concluded that the differences in the morphological development between the mono-species simulation and the multi-species simulation are relatively small. On the contrary, the in uence of interspecific competition on vegetation development is large, especially on the vegetation density. The extent to which the interspecific competition in uences the vegetation development depends on the type of competition. When considering no competition, the vegetation density of both salt marsh vegetation species can grow towards their maximum carrying capacity. When considering equal competition, the Spartina species has an advantage caused by its higher maximum carrying capacity, which results in a decrease in the vegetation density for the Salicornia species compared to the mono-species simulation. When considering spatial competition, both salt marsh vegetation species grow till they meet their combined maximum carrying capacity, which results in a decrease in the mean vegetation density for both species compared to the mono-species simulation. When considering the vegetation cover, the Salicornia species proves to be more constant during the different simulations (i.e. the change in vegetation cover is limited). The vegetation cover of the Spartina species is more strongly affected by the competition. When considering interspecific competition the vegetation cover decreases compared to the mono-species run. This research gives insight into the interspecific competition between different salt marsh vegetation species and shows the importance of the inclusion of interspecific competition on the vegetation development. Likewise, it has set the foundation for (long-term) simulations of a multi-species salt marsh, which can contribute to the construction of artificial salt marshes. |
| Item Type: | Essay (Master) |
| Faculty: | ET: Engineering Technology |
| Programme: | Civil Engineering and Management MSc (60026) |
| Link to this item: | https://purl.utwente.nl/essays/83182 |
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