Biodiversity-ecosystem functional relationships in evolved spatially structured societies

Project description

The most well known conclusion from studies of the relationship between biodiversity and ecosystem functions, supported by several experiments, is that productivity increases with the diversity of the flora. The first experiment showing this relationship was conducted in small fields in Minnesota, USA, which were sown with different numbers of plant species selected randomly from the plants that naturally appear in the immediate area. Productivity was shown to increase with the number of plant species, while the amount of nitrogen in the soil – the nutrients limited to the plants – decreased. This suggested that plant communities with greater plant wealth are better at using limited resources. To date, over 100 experiments and over 250 field studies have supported this relationship.

While the empirical support for the relationship between species richness and productivity is clear, this does necessarily mean that ecosystems with greater species richness are necessarily more productive. The experiments that have been conducted have usually investigated the effect of randomly composed communities over a relatively short period of time. These plant communities have also had to be artificially established by means of regularly clearing out weeds and other invasive species. The connection that has been seen therefore does not have to apply between different areas of the Earth, which differ both in environmental conditions and in evolutionary history. In fact, there are also often other correlations in field studies across large geographical areas, usually that productivity first increases with species richness and then decreases. A well-known overview article co-published by a large number of researchers suggested one way to reconcile these different perspectives was by seeing them as two sides of the same coin. However, this would require us to develop a theory for how biodiversity arises and is maintained in different parts of planet Earth.

The relationship between biodiversity and ecosystem functions has also been investigated in a small number of cases using dynamic models. A well-known model of species competing for two resources has been shown to recreate the relationships between biodiversity and productivity as seen in the experiment in fields in Minnesota, USA. In this model, it is assumed that resources are available in different amounts in different parts of the room. There are good reasons to believe from this and other studies that spatial heterogeneity is crucial for the emergence and maintenance of biodiversity. However, the models used so far to study the relationship between biodiversity and ecosystem functions have had several limitations. They have not encompassed ecological gradients or more realistic spatial structure. It is particularly important that so far the models have only included ecological processes, even though evolutionary processes are crucial for the emergence of biodiversity.

In this project, we intend to conduct the first theoretical study of the relationship between biodiversity and ecosystem functions in plant communities arising from the evolutionary process along heterogeneous landscapes. Our study will clarify how environmental and ecological factors contribute to biodiversity along with how they affect ecosystem functions.

The proposed project is based on an earlier grant to us from the Swedish Research Council (2015-03917 to ÅB with SD as co-applicant). It is our belief that our expected progress will prove vitally important in developing a synthetic theory for the relationship between biodiversity and ecosystem functions.