The PaNDiv experiment is a large field experiment in Münchenbuchsee (near Bern) which investigates the mechanisms by which nitrogen enrichment affects ecosystem functioning. N enrichment changes soil chemistry and directly increases plant growth and ecosystem productivity. At the same time, it can indirectly affect ecosystem function by causing a loss of plant species richness, a shift in functional trait composition towards fast growing plant species and an increase in the abundance of plant enemies such as foliar fungal pathogens. While we know a lot about the effects of biodiversity on function, we know much less about how important it is relative to these other drivers. In addition, functional composition effects have mostly been explored in observational studies where fertility and productivity covary with gradients in resource traits. By experimentally manipulating functional composition we can isolate its effects and compare them with diversity and fertility effects.
The PaNDiv experiment factorially manipulates N addition (0, 100kg N ha-1y-1), plant species richness (1, 4, 8 or 20 species), functional composition (two pools of fast and slow growing species defined based on leaf economic traits) and fungal pathogens (using fungicide) on 336 2m x 2m plots, which were sown in autumn 2015. We measure a range of ecosystem functions related to productivity, biogeochemical cycling and litter decomposition on these plots. We also monitor the diversity and abundance of the foliar pathogen communities to test a number of hypotheses about when pathogens have large impacts on plant communities. We have started further work to determine how changes in the plant community cascade to affect other groups including soil arthropods (Collembola and mites) and aboveground insects.
Tosca Mannall, Caroline Daniel, Thu Zar Nwe, Géraldine Chavey, Nadia Maaroufi, Anne Kempel and Anita Streit work on this experiment. Hugo Vincent and Mervi Laitinen are in charge of running the experiment.
In addition, we collaborate with researchers in Seville (Oscar Godoy and Rodrigo Granjel) to determine coexistence mechanisms (niche and fitness differences) and how these are affected by fungicide and nitrogen treatments and with researchers in Aarhus (Signe Normand, Urs Treier and Bjarke Madsen) who aim to distinguish differences in community composition and diversity from remote sensing.
We are always open to further collaborations, so just get in touch if you are interested.
For students of UNIBE: We often need helping hands. If you have some botanical knowledge and are interested in getting job opportunities, please contact hugo.vincent[at]ips.unibe.ch and we will put you on our mailing list.
Header photograph taken by Hugo Vincent ©. For more impressions, please visit our Gallery!