A couple of months ago our team was joined by the new PhD-student Hao Tang from China. Hao did his Master at the Sichuan Agricultural University and studied how rice can be used to remove heavy metals from contaminated soil. He is now doing his PhD in Hamburg and spent the first few months over here to read a lot about salt marsh ecology. For his PhD-thesis he now picked the topic of carbon sequestration in salt marshes. He will build on the work of Peter Müller and focus on the effect of hydrology on carbon sequestration. In his first experiment he is going to transplant different salt marsh vegetation into mesocosms in our tidal basins at the university. He will then use different flooding treatments to simulate sea level rise and see how it affects plant, soil respiration and microbial activity. Furthermore, he is going to study how grazing affects soil hydrology and how this in turn affects carbon sequestration in different soil layers in the field.
During my PhD when I went to conferences or met people at a statistics course they often remembered me as the person talking about horses and cattle all the time. Indeed, almost all the chapters of my PhD-thesis dealt with the question how grazing management with different livestock species and stocking densities affected some aspect of vegetation or other . However, I was not alone in this project and my colleagues Freek Mandema and Roel van Klink answered similar questions but with regard to birds and invertebrates in our grazing experiment in Noord-Friesland Buitendijks. After we all finished our PhDs the project was continued by Georgette Lagendijk and together we now published a new paper summarizing and integrating effects of the grazing treatments on biodiversity across trophic levels:
van Klink, R., Nolte, S., Mandema, F.S., Lagendijk, D.D.G., WallisDeVries, M.F., Bakker, J.P., Esselink, P., Smit, C. (2016): Effects of grazing management on biodiversity across trophic levels–The importance of livestock species and stocking density in salt marshes. Agric. Ecosyst. Environ. 235, 329–339. doi:10.1016/j.agee.2016.11.001
This summer I have been on a research trip to the Fudan University in Shanghai China. I was invited by Prof. Jihua Wu and Prof. Bo Li to spend a month at the Key Laboratory for Biodiversity Science and Ecological Engineering.
It was a very interesting trip indeed! PhD-student Zaichao Yang helped me to collect quite some cool data in the Dongtan marsh on Chongming Island (in a very short time!). Being used to our Wadden Sea marshes over here, I soon found out that the Chinese marshes are very different. The vegetation diversity is very low, there are crabs everywhere and the soil is very different, too. The soil, or to be more precise the organic carbon in the soil, was also the main focus of the study we did together. Within the southern part of the marsh, which is grazed by cattle, Zaichao established exclosures in 2014. He already collected a lot of data and compared accretion rates and the soil fauna community between the grazed and ungrazed treatment.
How about doing a PhD on salt marsh bio-geomorphology in Hamburg?
This is very exciting news for me! Pending final approval of external funding we are going to start a project this autumn to study bio-geomorphology of Wadden Sea salt marshes. The idea is to setup morphodynamic models of a salt marsh which include the effect of vegetation. This has been previously done for other marsh systems, but there are no models available for Wadden Sea mainland salt marshes. Additionally, effects of heterogeneous vegetation patterns on sediment deposition and accretion are poorly understood. For example, models thus far mostly focused on homogeneous low marshes, but vegetation structure strongly differs between marsh zones and forms heterogeneous patterns. Most importantly, models also generally assumed that vegetation is static, while morphological marsh development is indeed also a main driver of vegetation succession, leading to changes in vegetation properties which in turn might also affect sediment dynamics.
In this project, we want to improve morphodynamic marsh models by integrating feedback loops between sediment and vegetation dynamics for salt marshes in the Wadden Sea. These models will be better able to predict marsh response to different climate change scenarios provided by other projects within the DFG priority program ‘Regional Sea Level Change and Society (SeaLevel)’.
Within this project there is one open position for a PhD-student who will be mainly working in Hamburg. The study site will be situated in the Wadden Sea National Park Schleswig Holstein. Furthermore, a one year stay at the University of Antwerp (Belgium) in the research group of Prof. Stijn Temmerman is planned for data analysis.
So, if you have an MSc-degree in ecology, geomorphology or another relevant field and would like to do your PhD with us in Hamburg, check the official job posting and send your letter, curriculum vitae, and copies of degree certificate(s) until 31.05.2016 to: firstname.lastname@example.org
Vegetation succession of low estuarine marshes is affected by distance to navigation channel and changes in water level
When I started to work at the University of Hamburg about two years ago, I also had the opportunity to discuss a lot of things with Christian Butzeck, the only other member of the group (then) interested in sediment dynamics. Christian worked on the marshes along the salinity gradient of the Elbe estuary and also investigated which factors determine the succession of the marsh vegetation. He found that in the salt and brackish zones, the area covered by high marshes increased substantially but decreased in the tidal freshwater zone, while that covered by low marshes decreased in all the salinity zones. The distance to the navigation channel was the main factor determining whether succession of low marshes would be progressive or regressive.
His findings were now published and can be found here:
Does physiological integration enable Elymus athericus to colonize an unsuitable habitat?
The grass Elymus athericus is spreading in Wadden Sea salt marshes and outcompetes species-rich communities. We would like to investigate whether Elymus is able to invade apparently unsuitable habitats, because the mother plant is supporting daughter ramets via physiological integration through the rhizome. This will be done in a greenhouse experiment at the University of Hamburg. Plants from the island Schiermonnikoog were provided by co-supervisor Dr. Chris Smit (RUG).
Installing the experiment in the greenhouse (see Fig.), recording morphological and physiological plant parameters, 15N-labelling, measuring 15N-signature in plant material (mass-spectrometer).
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This year we are going to investigate how livestock grazing affects vegetation diversity in salt marshes. This topic has already been widely studied; however, how livestock grazing might interact with other factors is often unknown. Therefore we are planning to include the factors scale and topography an study how they interact with the effect of livestock grazing on vegetation diversity. This research will be conducted within the framework of the INTERFACE project by two new team members, namely Jennifer Ahrens and Thea Wahlers.