2 PhD positions in Ecosystem modelling of plant-soil feedbacks 80 %

Grasslands are highly diverse ecosystems that provide important ecosystem functions. Maintaining or restoring grassland biodiversity increases their ability to deal with environmental disturbances such as fires and droughts, which are expected to increase in frequency and severity in the coming century. However, our understanding of the mechanisms creating and maintaining the high species diversity in grasslands remain poorly understood, impeding the design of successful management strategies. An increasing body of evidence suggests, however, that interactions between plants and the community of soil organisms create plant-soil feedbacks that play a crucial role in creating and maintaining grassland biodiversity.
A new collaborative project between the University of Zurich and the University of Kansas (USA) aims to advance our understanding of how plant-soil feedbacks contribute to the functioning of grassland ecosystems. The research team in Zurich (consisting of 2 PhD students, an outreach coordinator and the PI) will develop and analyze mathematical models that quantify the interactions between plant and soil communities. These models will be calibrated and validated with the results of greenhouse experiments and long-term field experiments conducted with north American grassland species. The project aims to improve our fundamental understanding of grassland ecosystem functioning, which can then be used in conservation, restoration and education in the USA and Switzerland.
We invite candidates to apply for (one of) the two positions listed below:

PhD Position 1: Theory and tests of plant-soil feedback: implications for long-term dynamics
Your tasks:
1) Develop a model-data integration framework: Using data from many experiments with two North Carolina grassland species, you will develop and validate a mathematical model that describes how the soil community builds up over time, and how these soil dynamics affect the two plant species.
2) Extend this framework to multiple species: Using data from experiments that will be conducted with six Kansas grassland species, and recent theoretical advances to describe community-level plant-soil feedbacks, you will extend the applicability of the framework to more than two species.
3) Integrate findings with community-level models of plant-soil feedback: You will integrate the framework with the findings of the other PhD student project, which focuses on describing the consequences of plant-soil feedback on plant community dynamics.

PhD Position 2: Theory and tests of plant-soil feedback: implications for plant community dynamics
Your tasks:
1) Model the benefits of plant community diversity for ecosystem functioning: Using data from a long-term biodiversity field experiment, you will parameterize a model in which plant community dynamics are structured by plant-soil feedbacks. Model analysis will focus on how plant community diversity is created and maintained by plant-soil feedback, and how this affects ecosystem functions such as productivity.
2) Model impacts of dispersal limitation on biodiversity and ecosystem function: You will study to what extent previously unexplained trends in the experimental data can be modelled by incorporation of dispersal constraints and their impact on plant-soil community interactions and plant competition.
3) Integrate findings with dynamical soil community models of plant-soil feedback: You will integrate the multi-species model framework that includes dispersal constraints with the findings of the other PhD student project, which focuses on describing the consequences of plant-soil feedback on long-term dynamics.

For both PhD positions, the findings of each of the three tasks are expected to be reported in three scientific articles. These articles will then form the basis of the PhD thesis, and an education module for Swiss and American high school students, which will be developed by the PIs and the project's outreach coordinator.