Climate warming is especially pronounced in Arctic regions, where ecosystems are experiencing stronger and faster changes than the global average. This leads not only to rising temperatures but also to more frequent and intense extreme events, such as heat waves and droughts. Arctic soil microbes are directly affected by warming and indirectly influenced through changes in plant inputs and soil moisture. Microbial communities are central to ecosystem functions, including carbon and nutrient cycling, yet we still lack detailed knowledge of how warming and its indirect effects—such as drought and altered litter inputs—shape microbial thermal traits and activity. This project aims to address this knowledge gap using field warming experiments in Abisko, Sweden.
Supervisors: Honorine Dumontel & Johannes Rousk
Objectives
We are establishing field experiments to test how warming affects microbial thermal traits and how indirect warming effects—such as changes in plant inputs and drought—modulate microbial responses. We will study these effects using a soil warming experiment in Abisko, northern Sweden: AWRORE (Arctic Warming Responses to Organic matter and Reduced precipitation Experiment).
Here, many interesting thesis questions could be posed, potential research questions include:
- How do direct warming effects and indirect effects (drought and/or litter addition) shift microbial thermal traits? Do these changes alter microbial nutrient limitation?
- Are shifts in microbial thermal traits driven more strongly by temperature itself or by warming-induced changes in substrate availability?
- Does reduced precipitation modify microbial temperature responses under summer warming?
- Does warming influence microbial litter decomposition and associated carbon cycling processes?
- How do drying–rewetting events affect microbial growth and respiration across different warming treatments?
- Does prior exposure to warming alter microbial resistance or resilience to drying–rewetting pulses?
- Above-belowground interactions : How do warming-induced changes in soil microbes influence plant–microbe interactions?
The main things we will test are microbial temperature responses (growth and respiration) under a range of field treatments that combine seasonal effects (summer, winter, and chronic warming), drought, warming intensity (summer vs. extreme summer warming), and litter addition.
We will be very interested in talking more about your own questions and interest to developed a project.
Skills and techniques acquired
- Field work (setup the warming experiment, sampling, NDVI and LiCor measurements)
- Measuring bacterial and fungal growth rates using isotope tracing
- Estimating soil respiration using gas chromatography
- Soil physicochemical analyses (moisture, C, N, pH, organic matter, etc.)
- Assess microbial community composition
- Search and compile relevant literature within the topic
- Data processing and statistical analysis
Master’s Thesis Timeline (Field and Laboratory Work)
June 2026: Fieldwork in Abisko – experiment setup, sampling, and measurements (1 week); lab work on bacterial temperature dependences (~2 weeks)
July 2026: Fieldwork in Abisko – sampling and measurements (1 week); lab work on bacterial temperature dependences (~2 weeks)
August 2026: Fieldwork in Abisko – experiment setup, sampling, and measurements (1 week); lab incubation and measurements of bacteria, fungi, and respiration temperature dependences (~1 month)
Autumn 2026. Thesis.
Required knowledge
Strong interest in soil and microbial ecology. No prior experience required; training will be provided.
Application process
If you are interested, please contact: Honorine Dumontel, honorine.dumontel@biol.lu.se and/or Johannes Rousk, johannes.rousk@biol.lu.se