Understanding the mechanisms behind plant biodiversity is a key challenge in the context of global change. Modern coexistence theory has unified the processes driving plants interactions in two main mechanisms: niche differences (stabilizing) and competitive abilities, also called fitness differences (equalizing). These mechanisms have been mostly used to determine pairwise coexistence between species. However, a recent study by Saavedra et al. 2017, offered a conceptual framework to go beyond these pairwise interactions, enabling quantifying the impact of indirect interactions on plant species coexistence.
Niche differences and competitive ability differences for triplets of perennial plant species have been assessed in a previous grassland experiment in PaNDiv. A new experiment has been set up in Spring 2021 in Ostermundigen, using these results to build communities of three plant species following a gradient of niche differences and indirect interactions. Some communities are coexisting, with both large niche differences and small competitive abilities differences, while others are more “competitive”, coexistence remaining possible thanks to indirect interactions. This experiment also manipulates nitrogen addition, as resources limitation is an important driver of niche and fitness differences.
The aim of the project is to link the mechanisms behind the coexistence of these triplets (higher-order and indirect interaction, for example) to diverse measures of biodiversity functioning: biomass production, pathogen infection and herbivory, soil functioning, etc.…
Some possible projects could be:
– Measuring pathogen and herbivory damage and linking it to plant species coexistence
– Assessing the impact of nitrogen addition on the indirect interactions between species
– Characterizing soil functioning (soil carbon, soil nutrients, soil respiration and litter decomposition) and how it drives niche and fitness differences between species.
The internship will take place at the Institute for plant sciences, in Bern, Switzerland. The internship will be supervised by Pr. Eric Allan and Caroline Daniel. The duration is quite flexible, between 4-6 months from April 2022. An Erasmus+ grant application can be considered in order to cover living expenses. A good written and spoken English level is required.
Many other projects could be discussed, for more information, you can contact [email protected]