Climate warming is driving rapid shrub expansion across Arctic and sub-Arctic ecosystems, altering vegetation dynamics and ecosystem functioning. Shrubs can affect soil microbial composition and activity through litter and root exudate inputs, with consequences for nutrient cycling and the establishment of other plant species. Differences in these inputs among shrub types may therefore lead to contrasting outcomes, with deciduous shrubs potentially facilitating tree seedling establishment and evergreen shrubs favoring their own persistence. Distinct rainfall patterns may influence the expansion of different shrub types. However, the role of soil microbes under shrub expansion in shaping soil nutrient cycling and tree responses under changing rainfall patterns remains unclear.
Objectives
This project will use samples from a field experiment in Abisko, northern Sweden, to investigate how deciduous and evergreen shrubs influence soil microbial communities and functioning under different rainfall conditions. We will measure bacterial and fungal growth, soil respiration, nitrogen mineralization and nitrification, microbial community composition, and soil C and N properties. We will also characterize the rate and chemical composition of root exudates to explore the relationship between plant carbon inputs and soil microbial processes. These measurements will be combined with a greenhouse experiment to determine how shrub-induced changes in soil properties affect tree seedling growth and establishment. We aim to understand how different types of Arctic shrub expansion may shape belowground processes and, in turn, influence future tree establishment under changing climate and rainfall regimes.
Supervisors: Yichen Zhou & Johannes Rousk
Depending on the student’s interests and experience, research activities may include:
- Measuring bacterial and fungal growth rates using isotope tracing
- Measuring soil respiration using gas chromatography
- Assessing microbial abundance and community composition using DNA extraction, qPCR, and amplicon sequencing
- Quantifying root exudate release and chemical composition
- Measuring leaf and root functional traits, including morphological traits, C and N concentrations
- Conducting soil physicochemical analyses, including soil moisture, total C and N contents, pH, and organic matter
- Setting up and maintaining greenhouse experiments
- Searching for and reviewing relevant scientific literature
- Conducting data processing and statistical analyses
Required knowledge
Strong interest in plant ecology, soil ecology, and plant-soil-microbe interactions. No prior experience required; training will be provided.
This project can be taken for 15–30 credits.
Application process
If you are interested, please contact: Yichen Zhou, yichen.zhou@biol.lu.se and/or Johannes Rousk, johannes.rousk@biol.lu.se