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List of suggestions Bachelor and Master theses

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List for Bachelor's and Master's theses topics 2023/2024 (in English):
Themenliste59_englisch.pdf (145 KB)  vom 31.10.2024

If you are interested, please send an e-mail to Prof. Bruelheide (helge.bruelheide@botanik.uni-halle.de) or Dr. Dietrich (peter.dietrich@botanik.uni-halle.de).

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. 5) 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 tree species richness, mycorrhizal type and leaf litter on soil characteristics in a tree diversity experiment (Peter Dietrich)
The plots of the MyDiv experiment (for description see no. 5) were covered with a tarp during establishment to prevent the growth of ‘weeds’. The tarp was removed in November 2022, but there is still tarp in a small part of the plots. This tarp is used for the so-called ‘TreeRex’ experiment. A certain amount of leaf litter is deposited under one part of the tarp every year, while there is no leaf litter in the other part of the tarp area. The aim is to see what influence leaf litter (as well as tree species richness and mycorrhizal type) has on nutrient cycles and food webs. This work will examine whether and how soil characteristics, such as soil pH, nitrogen and phosphorus content, differ between the plots. The soil samples have already been taken and sieved. Analyses can start in January 2025.

Microscopic-anatomical studies

8.    The influence of fertilisation, light and competition on the anomalous secondary thickness growth of Atriplex sagittata (Peter Dietrich, Heike Heklau)
In a greenhouse experiment that was conducted from February to November 2024, we grew Atriplex sagittata plants under different conditions - low or high levels of light, fertilisation or no fertilisation, with or without competition (all possible combinations). The aim of this study is to see how these factors affect the abnormal secondary thickness growth and when in the development of the plant. Samples have already been taken and can be analysed starting in January 2025.

Invasion biology

9.    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).

10.    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.

Interactions between plants and soil fauna

11.    How diverse are green roofs? (Peter Dietrich in co-operation with the UFZ Leipzig)
In times of climate change and biodiversity loss, new methods of protecting nature are urgently needed. One idea is green roofs, which are not only refuges for rare species, but could also be a crucial factor for air quality and climate in cities. The Helmholtz Centre for Environmental Research in Leipzig is home to a green roof research facility (https://www.ufz.de/index.php?de=44676   ), which aims to find out which type of green roof is most effective and whether rare species really can be found on green roofs. The main aim of this project is to analyse the soil fauna (can rare fungi be found in addition to rare plants? Assessing soil health with the help of nematodes). Studies can start in spring 2025.

BEF-China / TreeDì / BrazilDry / IDENT network

12.    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.

13.    Interactions of endophytic and pathogenic leaf fungi with herbivory in the MyDiv experiment (Michael Koehler, Peter Dietrich, 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.

14.    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.

Biodiversity trends in Germany

15.    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.

16.    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.

17.    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.

18.    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   ).

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