Forest Entomology ¶

There are several open Master theses in the forest entomology group, if interested, please contact the person mentioned in the respective description.

We are open to applications for Bachelor's theses, and, subject to agreement, it may be possible to convert a Master's thesis work into a Bachelor's thesis work.

Title: Change of diversity and food-web structure in response to macro- and micro-climate and forest management

Abstract: Land-use and climate change are major drivers of global biodiversity loss. As biodiversity at multiple trophic levels is important for multifunctionality of ecosystems, changes in community composition and species interaction networks (food-webs) will likely challenge ecosystem functioning and stability. Understanding and predicting these effects is important, especially in complex landscapes such as forests, where aquatic and terrestrial communities are interconnected, but might respond differently to global change. This project aims to (1) identify litter-dwelling invertebrates that have been collected in streams, riparian and terrestrial systems at 12 managed and unmanaged sites acoss Switzerland, (2) identify food-webs based on already existing stable isotope data, (3) assess and quantify the effects of temperature and management on aquatic, terrestrial and interconnected communities and food-webs in forests. In order to answer these questions, you will work mainly with existing samples and therefore no field work will be involved. However, it is possible to visit the places where the samples were taken and additional field work can be discussed. You will also get insights into stable isotope analyses.

Supervisor and Co-Supervisor: Martin Gossner and PhD student Bastiaan Drost

Prerequisites: Are you interested in food webs, leaf litter communities, invertebrate identification, stable isotope analysis? Then this is exactly the right Master's thesis for you! The results of the MSc-project are expected to be published in a peer-reviewed scientific journal. You should have some basic skills in statistics with R.

Finance: no extra costs need to be covered

Contact (e-mail): martin.gossner(at)wsl.ch

Project website: Initiative WSL-Eawag; Project: Food-webs across aquatic-terrestrial environments in forests in the face of climate change

Date modified: 28. Jan. 2025

Title: Global change effects on decomposer communities and decomposition

Abstract: We proposed a global protocol to assess human impacts on forest ecosystems using experimental microcosms. The main question we aim to address is: How do current and future climatic conditions, forest habitat degradation and management, influence biodiversity and ecosystem functioning in water filled microcosms worldwide? In the Master's thesis offered, you will assess and analyse data of this global experiment with a focus on Swiss study sites. This will increase our understanding of the impacts of global change drivers on ecosystem functioning in Switzerland. Recommendations for stakeholders and practitioners will be derived. No field work is required, but it is possible to conduct a small experiment and visit the places where we collected the data. Also identification and measurements of insect larvae from additional samples is possible. There is the opportunity to contribute your own ideas.

Supervisor: Martin Gossner

Prerequisites: Bachelor’s degree in biology, ecology, or environmental sciences; strong interest in ecosystem relationships; fluent in German and/or English; eager to work with insects and do statistical analyses; experience in statistics and R is advantageous and necessary.

Finance: no additional costs

Contact (e-mail): martin.gossner(at)wsl.ch

Project website: MICROcosm Protokoll

Date modified: 28. Jan. 2025

Title: Effect of tree drought memory on insect diversity and performance

Abstract: Extreme droughts can have long‐lasting effects on forest community dynamics and species interactions. There is increasing evidence that trees that have experienced extreme drought effects in the past show differences in their leaf chemical profile compared to trees that have not been exposed to drought. Such drought memory effects are likely modulating the interaction between trees and insect herbivores whose community composition and performance is driven by leaf chemistry. Yet, our understanding of how drought memory effects on tree chemistry modulates ecological relationships between trees and insects is just unfolding.

Supervisor and Co-Supervisor: Martin Gossner and Dr. Michael Eisenring

Prerequisites: We offer an MSc project in the forest entomology group at WSL (part of the ETH domain) in Birmensdorf in collaboration with the Technical University of Munic (TUM). Making use of a large drought stress experiment near Munich, the MSc student will compare the insect communities in European Beech trees that have previously been experimentally drought stressed with trees that have not been exposed to drought. Moreover, the student will conduct experiments with caterpillars and aphids to test if insects perform differently on previously drought stressed trees vs. non-stressed trees. The study will be conducted in early summer 2025. Ideal project start is April 2025. You should have a strong interest in plant-insect interactions and insect taxonomy (sorting of sampled insects will be required). Basic skills in statistics with R are advantageous.

Season: Spring, Summer

Abroad: yes

Finance: travel costs will be covered

Contact (e-mail): michael.eisenring(at)wsl.ch

Date modified: 28. Jan. 2025

Title: The Effect of Within-tree Microclimatic Gradients on Oak Phenology & Oak-Herbivore Interactions

Abstract: The relationships between plants and insect herbivores are largely mediated by phytochemical traits. Therefore, factors that substantially alter phytochemistry may have wide-reaching ecosystem-level consequences. Due to their size and vertical stratification mature trees possess pronounced vertical gradients in temperature and light conditions. These within-tree microclimatic gradients have been associated with variation in leaf chemistry and herbivory. In addition, climate change is expected to also alter forest microclimate with far reaching ecological consequences. This project is designed to use Oak (Q.robur) to quantify the relationship between within-tree microclimatic variation, phytochemistry and herbivory and to understand to what extent light and temperature gradients contribute to within-tree variation in leaf phenology, chemistry, and herbivory. 

The thesis starts in March/April 2025 (flexible starting date possible).

This project will be performed in controlled environments in climate chambers at the ETH Zurich. We will use Pedunculate oak (Quercus robur) clones and grow them in different climate chambers simulating the upper canopy, lower canopy or ground-level light intensity and temperatures mirroring the natural microclimatic conditions measured in canopy forest during field experiment in 2024. By observing the trees throughout the growing season, we will measure growth-related traits (leaf number, flushes SLA leaf specific area), assess trees’ resistance to herbivory by performing herbivore bioassays with caterpillars, and measure leaf defense chemistry. Consequently, the candidate will gain trainings in plant and insect phenotyping, insect bioassays and plant metabolomics including sample preparation, processing, and phytochemical analyses. 

Working Breakdown: climate chamber: 60 %, lab work: 20%, office work: 20%

Supervisor and Co-Supervisors: Martin Gossner and Dr. Michael Eisenring & Dr. Moe Bakhtiari

Prerequisites: The candidate should have a strong interest in plant-insect interactions. Basic skills in statistics with R are advantageous. In-depth knowledge in analytical chemistry is not mandatory for this project.

Finance: travel costs will be covered

Contact (e-mail): mojtaba.bakhtiari(at)wsl.ch

Project website: https://www.uni-marburg.de/en/fb17/phytoakmeter

Date modified: 28. Jan. 2025

Title: Exploring the impact of latitudinal gradients & drought on oak phytochemical diversity and its consequences on herbivory 

Abstract: The relationships between plants and insect herbivores are largely mediated by phytochemical traits. Therefore, factors that substantially alter phytochemistry may have wide-reaching ecosystem-level consequences. Oak (Quercus robur), one of the most dominant broad-leaved trees in Europe is known to be highly plastic especially in relation to drought and heat condition, and environmentally induced changes could influence oak’s chemical phenotype and consequently its response to herbivory. This project aims to investigate whether it exists a site-specific phytochemical variation in oak trees along latitudinal gradient encompassing sites from southern to northern Europe and if so, does such variation drives variation in herbivory rates. By focusing on several pre-existing plots where oak clones have been grown in along a European latitudinal gradient from southern France to Northern Finland, over a decade ago, we will sample leaves for metabolomic analysis and conduct feeding bioassays with specialist and generalist chewing and sucking herbivores in the lab. This project will enrich our understanding on chemotypic differentiation in spatially separated tree populations, understanding their importance in herbivory resistance across spatial distributed populations.

The goal of this thesis is to test the following hypotheses:
1) Oak’s phytochemical composition is modulated by latitude and further controlled by local site-specific climatic conditions.
2) Specialist and generalist caterpillars and aphids perform differently when feeding on oaks grown at different sites encompassing varying phytochemical composition.
3) Oaks with higher phytochemical diversity profiles should show higher resistance to herbivores.

Start date and work involved: The thesis starts in April 2025 (flexible starting date possible). The thesis includes extensive field-work in Germany, France and possibly Finland.  The MSc student will conduct feeding assays with caterpillars & aphids on oak trees, quantifies different leaf physiological and chemical parameters and will analyze the results statistically. Consequently, the project will allow the candidate to gain experience in plant and insect phenotyping, herbivory quantification and state-of-the art plant metabolomics including sample preparation, processing, and phytochemical analyses.

Working Breakdown: field work: 60 %, lab work: 20%, office work: 20%.

Supervisor and Co-Supervisor: Martin Gossner and Dr. Michael Eisenring & Dr. Moe Bakhtiari

Prerequisites: The candidate should have a strong interest in plant-insect interactions and interest in conducting field work. Basic skills in statistics with R are advantageous. In-depth knowledge in analytical chemistry is not mandatory for this project.

Season: Spring, Summer

Abroad: yes

Finance: travel costs will be covered

Contact (e-mail): mojtaba.bakhtiari(at)wsl.ch

Project website: https://www.uni-marburg.de/en/fb17/phytoakmeter

Date modified: 28. Jan. 2025

Title: Change of food-web structure and food-chain length in response to ecosystem engineering by beavers

Abstract: The presence of beavers influences ecosystems and therefore species composition and interactions. As biodiversity at multiple trophic levels is important for the multifunctionality of ecosystems, changes in community composition and species interaction networks (food-webs) will likely challenge ecosystem functioning and stability. Understanding and predicting these effects is important, especially in complex blue-green habitats, where aquatic and terrestrial communities are interconnected, but might respond differently. This project aims to reconstruct food-webs in beaver ecosystems via bulk and/or compound-specific stable isotope and fatty acid analyses. In order to answer these questions, we have collected species data in beaver systems in Switzerland. Within the frame of the Master thesis taxa (species or higher) will be identified and stable isotopes and fatty acids will be analysed in the lab. The ultimate goal is to analyse changes in food-web structure and food-chain length in response to ecosystem engineering by beavers.

We offer an MSc project in the Forest Entomology Group in collaboration with the Community Ecology Group at WSL (part of the ETH domain) in Birmensdorf. The MSc project is part of the Blue Green Biodiversity research initiative of WSL and Eawag. The student acquires taxonomic knowledge about invertebrates and learns how to carry out stable isotope and fatty acid analyses as well as food web analyses. The study is independent of the growing season. 

Supervisor and Co-Supervisor: Martin Gossner and PD Dr. Anita Risch

Prerequisites: You should have a strong interest in laboratory work and statistical analysis and preferably already have knowledge of stable isotopes. Basic knowledge of statistics with R is an advantage.

Season: Spring, Summer

Contact (e-mail): martin.gossner(at)wsl.ch

Project website: https://www.wsl.ch/de/ueber-die-wsl/organisation/programme-und-initiativen/forschungsinitiative-blue-green-biodiversity/species-interactions-in-beaver-engineered-habitats-link-land-water-ecosystem-processes/

Date modified: 28. Jan. 2025

Title: Effects of climate and human footprint on invertebrate diversity in Phytotelmata: a global meta-regression 

Abstract: Ecology is a fast moving field of research, notably with the general use of global biodiversity datasets. Despite that natural aquatic microcosms such as pitcher plants, tank bromeliads, and water-filled tree holes have been proposed as excellent model ecosystems, their use to test macro-ecological patterns and the influence of global change factors on biodiversity has been restrained to specific regions (e.g., Latin America for tank-bromeliads), largely hampering the general insights we can get from such “microcosms”. With this master project, we propose to leverage this issue, in compiling global data about invertebrate diversity in Phytotelmata (pitcher plants, bamboo stems, tank bromeliads and tree holes). Some of these aquatic habitats are restrained to certain area, but other can be widespread (bamboostems, pitcher plants, and water-filled tree holes). Moreover, artificial analogues of tree holes come to complement natural observations. In conducting a global meta-regression based on a systematic survey of the literature, we aim to (i) describe natural global trends of invertebrate diversity (alpha, beta and gamma) in these different habitats (latitude, climate), and (ii) test if after having accounted for natural variations, we can use Phytotelmata as a unit ecosystem to assess the effects of global changes (e.g., human footprint). While this project is not involving fieldwork, we will make connections between the master candidate conducting this global meta-regression work with leading authors in ecology using these systems to conduct their research [P. Diane Srivastava (Vancouver, British Columbia); P. Gustavo Q. Romero (Sao Paulo, Brazil), Janna S. Petermann (Salzburg, Austria), Régis Céréghino (Toulouse, France)], which will be scientifically enlightening, and can open future opportunities for the candidate.

Supervisor and Co-Supervisor: Martin Gossner and Dr. Andreas Bruder, Dr. Thibault Rota

Prerequisites: The chosen candidate is expected to have a strong autonomy, and a taste for testing ecological theories applied to global change issues. Researchers of different career stages and covering all the aspects of the work will supervise the candidate, but the motivation of the candidate will be decisive up to its publication in a high-impact journal.

External: yes

Contact (e-mail): thibault.rota@supsi.ch

Date modified: 28. Jan. 2025

Title: Succession of arthropod diversity and species traits after the forest fire in Leuk

Abstract: In 2003, an extensive forest fire consumed over 300 hectares of woodland on a mountain slope near Leuk, Switzerland. This event stands as one of the most significant fire incidents of the past century in Switzerland, resulting in the near-complete elimination of all aboveground plant and most arthropod life across various forest ecosystems within the elevation range of 900 to 2100 meters above sea level. In response to this ecological disruption, pitfall and flight interception traps were established in the center, at the edge and in intact surrounding forests at different elevation. Over subsequent intervals of one, two, three, four, ten, and twenty years following the fire, the changes in arthropod communities were monitored.

The primary objective of this master's project is to analyze the temporal changes in species and functional diversity and to identify trait shifts along the succession after the disturbance. Therefore, a target group will be selected and identified to species level with the help of taxonomic specialists. Subsequently, the succession of diversity and traits will be modelled using an appropriate statistical framework.

Supervisor and Co-Supervisor: Martin Gossner and Dr. Marco Moretti

Prerequisites: You should have a strong interest in biodiversity and insects. Skills in statistics with R are advantageous. 

Contact (e-mail): martin.gossner(at)wsl.ch

Date modified: 28. Jan. 2025