By modifying the biotic and abiotic components of the soil they grow in, plants create soil legacies that can affect local species coexistence by moderating the relative performance of plant species in a community. These plant-soil feedbacks are often caused by a variety of mechanisms operating simultaneously such as resource preemption, root exudation, or changes in the structure and functioning of soil microbial communities. In recent years, much progress has been made in our understanding of soil microbial legacies and their contribution to plant population and community dynamics. However, the role played by soil chemical legacies in mediating plant-soil feedbacks has yet to be elucidated.
Soil chemical legacies arise from dynamic changes in the identity, diversity, and abundance of organic compounds present in the soil solution of a plant community, which can contain hundreds (if not thousands) of metabolites depending on the environmental context. Although recent evidence supports the fact that some plant species can react to soil chemical legacies by altering their root foraging, it is still unclear whether these chemical plant-soil feedbacks can moderate plant-plant interactions and affect local species coexistence. In addition, it is still unclear why some species react to soil chemical legacies and others do not. This is an important knowledge gap considering that, among all the mechanisms that plants use to interact with their biotic environment, many rely on the synthesis, release, and detection of chemical cues and signals by above- and belowground plant organs.
The main objective of this research project is to improve our understanding of plant species coexistence mechanisms by explicitly considering the role of soil chemical legacies in plant-soil feedbacks as well as its dependence on root economics. This objective will be investigated in the context of global environmental change (i.e., increased nitrogen availability) using grasslands as a model system. This project has three specific objectives: (1) investigating whether root economics can predict plant responses to soil chemical cues, (2) investigating the extent to which biotic (plant species richness) and abiotic (soil N availability) factors interactively affect soil chemical legacies, and (3) delivering new insights into the ecological consequences of soil chemical legacies by studying how changes in soil chemistry can feedback to the next generation of plants. All these research questions will be addressed using new experimental approaches and cutting-edge methods in functional and chemical ecology.