Martin Luther University Halle-Wittenberg

Gutianshan [(c) Christian Ristok]

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List of suggestions Bachelor and Master theses


List for Bachelor's and Master's theses topics 2023/2024 (in English):
Themenliste57_englisch.pdf (168.6 KB)  vom 07.06.2024

If you are interested, please send an e-mail to Prof. Bruelheide () or Dr. Dietrich ().

Biogeography

1. Area analyses of rare and endangered plant species on the Red List (Erik Welk)

More than 1000 species from the group of ferns and flowering plants are considered rare and/or endangered or threatened in the Federal Republic of Germany. The aim of a bachelor thesis would be to develop range models for selected species on the basis of environmental data. In this way, realistic and species-specific predictions for potential occurrence/disappearance can be developed, also in the context of climate change scenarios (also suitable for the winter semester).

2. Niche evolution of selected plant genera (Erik Welk)

For more and more genera of ferns and flowering plants, molecular-genetically based hypotheses on the relationship structure are available. If such 'phylogenies' are combined with precisely recorded distribution data of the species involved, it is possible to reconstruct the ecological-geographical differentiation and thus gain insights into evolutionary and speciation processes (also suitable for the winter semester).

3. Biogeography of the field flora of Mongolia (Erik Welk)

The segetal flora of Mongolia is very young, as large-scale agriculture has only been practised in this region for about 100 years. This provides an exciting opportunity to analyse the range types, relationships and trait combinations that form this species group and - in the case of master's theses - whether this recruitment was similar in neighbouring regions.

4. Comparison of biogeographical niche models based on databases or classical range maps (Erik Welk)
For numerous organism groups, digitally available distribution data (e.g. GBIF) are incomplete and very heterogeneous in terms of space and time. In addition, published distribution maps exist, which are spatially more complete but often less accurate due to the inclusion of heterogeneous information sources. Using a selection of plant species as an example, the aim of this work is to find out whether these differences significantly influence the results of niche analyses and modelling. The use of GIS, biodiversity databases and geostatistical methods will be learned (also suitable for the winter semester).

Biodiversity experiments

5. Influence of tree species richness and mycorrhizal types on leaf traits in a tree diversity experiment (Peter Dietrich, Tobias Proß)
The MyDiv experiment, located at the UFZ experimental station Bad Lauchstädt, aims to investigate the influence of tree species and mycorrhizal type diversity on forest ecosystem functioning. Previous studies have shown that species-rich forests produce more biomass than species-poor communities (i.e. "function" better), and that this can be explained, among other things, by a change in leaf characteristics with increasing diversity. The aim of this work is to test whether leaf traits (e.g. phosphorus, lignin, phenols, metals...) change with increasing diversity, and whether they differ in communities with different mycorrhizal types. The leaf samples are already dried and ground and can be analysed at any time.

6. Influence of tree species richness and mycorrhizal types on the composition and diversity of the herb layer in a tree diversity experiment (Peter Dietrich)
The plots of the MyDiv experiment (for description see no. 6) were equipped with a tarp during establishment to prevent the growth of "weeds". The tarp was removed in November 2022. The aim of this project is to determine the composition and diversity of the grasses and herbs growing in the areas in May 2024 in order to test the influence of tree species and mycorrhizal type diversity on the herb layer. Furthermore, the plants will be analysed with regard to functional characteristics and mycorrhisation. Potential start is May or September 2024.

7. Influence of plant species richness and long-term fertilisation on the root and leaf microbiome (Peter Dietrich, Michael Köhler)
The DivResource experiment, located at the UFZ experimental station Bad Lauchstädt, is a biodiversity experiment (1, 2 or 4 grass/herb species) with additional fertilisation treatment. Over the last 10 years, it has been observed that species-poor and fertilised plant communities develop differently from species-rich, unfertilised communities. One hypothesis is that the microbial communities that colonise the plants change due to loss of diversity and fertilisation, which in turn has an influence on the structure and productivity of the plant communities. The following topics can be selected: (1) analysis on the colonisation of roots with mycorrhiza by staining and microscopy; (2) analysis on plant microbiomes by DNA extraction and sequencing. The plant samples have already been taken and stored; you can start at any time.

8. Influence of functional plant diversity, mycorrhiza type and soil fauna on root characteristics and mycorrhization of trees (Peter Dietrich)
A tree experiment was conducted at the iDiv Ecotron in Bad Lauchstädt (https://www.idiv.de/de/forschung/plattformen-und-netzwerke/idiv-ecotron.html   ) in 2023 ("FunDrought experiment"). In this experiment, in which a large number of different institutions were involved (iDiv, Leipzig University, MLU, Leuphana University...), two tree species grew in each Ecotron chamber, which were either very similar (i.e. following the same characteristics/mycorrhizal strategies) or very dissimilar. Furthermore, the soil fauna was manipulated (with or without earthworms, spiders etc.). The aim of the bachelor thesis is: (1) measuring and analysing the root characteristics, (2) staining, measuring and analysing the colonisation of the roots with mycorrhiza. Work can start at any time.

9. Lignin, cellulose and hemicellulose contents of tree species in German biodiversity experiments (Helge Bruelheide, Tobias Proß).
Using leaf samples from the MyDiv, Kreinitz and BioTree experiments from about 15 tree species, the cell wall polymers will be analysed by wet chemistry and NIRS and correlated with the known leaf characteristics (SLA, LDMC, cation contents, leaf tensile strength, phenolic contents etc.). Furthermore, it will be analysed whether the contents depend on the different species richness of the plots and influence the herbivory by insects in the plots. The project is integrated into the TreeDì graduate school.

Microscopic-anatomical studies
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Invasion biology

10. The importance of climate change over the last century for the spread of neophytic plant species in Central Europe (Erik Welk, Helge Bruelheide)
The data from the floristic mapping in Germany make it possible to record the temporally increasing spread of some neophytic species quite well. Species often only spread over large areas several decades after their "arrival". The question is whether the species have had to adapt to the new environment during this time or whether climate change to date can explain the delay. The aim of the bachelor thesis is to compile and analyse the distribution areas of selected species and climate data series in order to come closer to answering the question (also suitable for the winter semester).

11. Phenological use of gaps as a cause of the dispersal success of neophytic species in North American forests (Erik Welk, Helge Bruelheide)
With the increasing availability of large amounts of georeferenced plant photos from citizen science projects and portals (iNaturalist, ...), possibilities arise to extract phenological processes (flowering, fruiting, seed dispersal, ...) from image data. By comparing the phenology of neophytic invasive species with data from the native flora, the aim is to test whether invasion success can be explained by exploiting phenological "gaps". Master's theses would also examine whether the phenological behaviour in the native area differs from that in the neophytic area.

Mycorrhizae and other endophytes

12. Effects of seed endophytes on the holobiome of plants and their alteration by drivers of global change (Peter Dietrich, Michael Köhler)
Seeds can harbour a variety of microbial endophytes. However, it is not clear whether these endophytes then also colonise the roots and leaves of the seedlings. To test this, the seed microbiome will first be detected and compared via DNA extraction and Illumina sequencing. Plants will then be grown under sterile conditions. These plants will be analysed with regard to their root and leaf microbiome (also via DNA sequencing) and then compared with the seed microbiome results. The seeds come from different biodiversity, fertilisation and drought experiments, so that it can be further tested whether these drivers of global change have an influence on the seed microbiome and thus on the holobiome of the plants.

Interactions between plants and soil fauna

13. Effects of plant species on soil characteristics and nematode communities (Peter Dietrich)
In the Jena experiment, one of the largest biodiversity experiments in the world, nematode communities were determined in 60 monocultures + soil samples were taken. The aim of this work is now to measure soil characteristics (phosphorus, potassium, pH) and to test whether the plant species-specific changes in soil characteristics can explain the different nematode communities in the monocultures. Soil samples have been stored and work can begin at any time.

14. How diverse are green roofs? (Peter Dietrich in cooperation with the UFZ Leipzig)
In times of climate change and biodiversity loss, new methods of protecting nature are urgently needed. One idea are green roofs, which are not only refuges for rare species, but could also be a key factor for air quality and climate in cities. The Helmholtz Centre for Environmental Research in Leipzig is running a green roof research facility (https://www.ufz.de/index.php?de=44676   ) to find out which type of green roof is most effective and whether rare species really can be found on roofs. In this project, the vegetation will be recorded and soil samples can be analysed with regard to soil biota (can rare fungi and other microbiota be found in addition to rare plants?) Initial investigations can start in autumn 2024

BEF-China / TreeDì / BrazilDry / IDENT network

15. Meta-genomics of leaf fungi of subtropical tree species (Michael Koehler, Tesfaye Wubet, Helge Bruelheide)
The tree species investigated in the TreeDì greenhouse experiment will be analysed for endophytic leaf fungi using Illumina barcoding. The aim is to answer the question of whether there is a spill-over effect from one tree species to another when two different tree species are cultivated closely together in one tube. The samples have already been taken so that molecular genetic analyses can be carried out immediately.

16. Interactions of endophytic and pathogenic leaf fungi with herbivory in the MyDiv experiment (Michael Koehler, Tesfaye Wubet, Helge Bruelheide)
In the MyDiv experiment, the diversity of leaf fungi was analysed using Illumina barcoding. Now the infestation rate of individual pathogens and the percentage of herbivory damage should be determined by means of visual identification. The aim is to investigate the interactions of leaf fungi with each other and to determine whether herbivory has an effect on fungal diversity and composition. The samples were taken in autumn 2021 so that the analyses can be carried out immediately.

17. Leaf as ecosystem - diversity and interaction of endophytic microbes (bacteria, protists, fungi) in leaves (Michael Koehler, Helge Bruelheide)
In different biodiversity experiments, leaf samples from shrubs and trees were collected to be analysed for different microbial communities. The aim of this study is to shed initial light on the interaction of as many different endophytic microorganisms as possible.

18. Analysis of 13C and 15N isotopes using infrared spectroscopy (Tobias Proß, Stefan Trogisch, Helge Bruelheide)
Leaf samples from the TreeDì graduate school greenhouse experiment were analysed for stable carbon and nitrogen isotopes. In a pilot study, an attempt will be made to calibrate these isotopes using infrared spectroscopy. The samples are available so that the analyses can be carried out immediately

Biodiversity trends in Germany

19. Temporal trends in grassland and forest vegetation in Europe (Ute Jandt, Helge Bruelheide)
There is an increasing number of resurvey studies on increases and decreases of species richness as well as of particular species in grassland and forest vegetation in Europe. The aim of this project is to compile all these studies and to carry out a meta-analysis on the temporal trends reported in this study. In addition, potential causes of biodiversity change will be retrieved from the original studies as well as from external sources, such as climate and land use data.

20. Analysis of the 50-year time series of the permanent plots on the Ochsenburg (Kyffhäuser) (Helge Bruelheide, Ute Jandt)
Since 1969, Klaus Helmecke has recorded the exact position of plant individuals on five 1 m2 permanent plots. The aim of the analysis of this unique time series is to analyse the spatio-temporal dynamics of the various plant species. In particular, the migration of individual plants within the plots will be analysed. This work requires solid knowledge of the statistics programme R.

21. Relationship between the moss cenoses of the iSPOT permanent plots and soil conditions (porphyry outcrops near Halle) (Ute Jandt, Susanne Horka, Helge Bruelheide)
As part of the repeat investigations of the porphyry knolls near Halle, numerous permanent plots were created in which all moss and lichen species were recorded. The aim of this work is to determine the moss species in the areas on the basis of samples already taken and to analyse the relationship with the soil conditions that have also already been determined. Previous knowledge of cryptogam determination is required.

22. Analysis of biotope mapping data to record and analyse plant species trends (Helge Bruelheide, Lina Lüttgert, Reinhard Klenke, Florian Jansen).
The data from repeated biotope mapping of a federal state should be analysed in order to establish temporal trends of the plant species occurring there. The main focus of the work is on data preparation, and various analysis methods can then be used to establish species trends and characterise winners and losers, e.g. on the basis of their functional characteristics. The work is being carried out as part of the current iDiv project sMon (https://www.idiv.de/de/smon.html   ).

Sustainability of agriculture

23. Research on the potential of vertical farming (Peter Dietrich in collaboration with Rosario Iacono (UFZ))
This thesis explores the transformative role of mycorrhizae in boosting crop yield, enhancing product quality, and improving plant adaptation within vertical farming systems. By integrating these beneficial fungi into hydroponic setups, the research aims to significantly reduce fertilizer dependency, cutting costs and increasing sustainability. Vertical farming not only promises to revolutionize urban agriculture but also to free up traditional farmland, aiding in the restoration of natural environments. This study seeks to fill the knowledge gap on mycorrhizae's potential in vertical farming, offering innovative solutions for a greener and more efficient future in food production.

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