A central question in plant ecology is which plant species can co-occur in a community, sharing the same set of resources. In principle, species with superior competitive abilities might displace other species by reducing resources to levels where their competitors cannot exist anymore, thereby reducing the diversity in plant communities.
Empirical evidence shows, however, that often more species than might be expected in fact coexist. It has been proposed that this is the case because even a species very efficiently acquiring a resource will not be able to reduce the availability of this resource to plant individuals that are far away. In this case, the strength with which individuals can compete will be determined by the degree to which the resource pools accessible to competing individuals (e.g. soil nutrients) are connected, i.e. the rate with which e.g. nutrients are transported between the two. When transport is strongly limited, individuals will be more separated in terms of competition for these nutrients, i.e. their coexistence will be facilitated.
To date, the e?ects of nutrient transport rates on the strength of plant competitive interactions has only been explored in mathematical models, probably because manipulations of transport limitations in "real" soils are difficult to achieve due to the multitude of ways in which nutrients move in soils. In the present project, we propose experimental manipulations of nutrient transport in experimental plant communities to test for their effects on the performance of their component individuals and on the strength of their competitive interactions. We will assess nutrient transport between individuals using isotopic and statistical approaches, and test whether the strength of their interactions correlates with measured transport rates as predicted by competition theories. The proposed experimental manipulations and the analysis of their consequences are relevant from a basic science and an applied perspective, especially since agricultural soil management alters the mechanisms addressed in this project.