Why diversity?
Meadows can consist of a few or of very many plant species. Does that make a difference to how an ecosystem functions? This question is at the heart of the Jena Experiment, one of the largest and longest-running biodiversity experiments in the world. Since 2002, meadows deliberately sown with 1 to 60 plant species have been growing on around 80 experimental plots in the floodplain of the river Saale near Jena. Because the plots differ only in their number of species, we can measure directly what diversity does. The result after more than twenty years: species-rich meadows produce more biomass, store more carbon and are home to more animals.
Our subproject: insects and what they do
Thousands of invertebrates live in a meadow. Some feed on plants, such as grasshoppers, leafhoppers and aphids. Others feed on these plant eaters, such as spiders and ground beetles. Feeding on plants (herbivory) and preying on other animals (predation) are key processes in an ecosystem: they determine how much plant material remains and whether individual species multiply en masse.
Our previous work shows that more plant species also mean more animal species and more herbivory and predation. It also shows, however, that insect communities fluctuate strongly from year to year and within a year. In the current subproject we therefore ask:
What causes these fluctuations?
Does plant diversity act as a buffer, so that insect communities and their functions remain more stable in species-rich meadows, especially in dry years?
In view of climate change, this is of practical importance: if diversity stabilises, species-rich meadows are better protected against extreme years.
How we work
We combine two approaches. In the field, we record insects and spiders and measure herbivory and predation on the experimental plots. Together with data from earlier years, this yields time series spanning more than 15 years, which we analyse statistically.
In the greenhouse, we test the mechanisms under controlled conditions. In the HerbiCoMic experiment, a trial with around 900 pots, we study the interplay of drought stress, plant diversity and herbivores. We expose small plant communities with different numbers of species in their pots to above- and below-ground plant eaters (caterpillars and beetle grubs) and to drought, and measure how much of the plants is eaten and how they grow. We also study the survival and growth of the herbivores.
Key facts
Lead: Sebastian T. Meyer together with Anne Ebeling (University of Jena) · Funding: DFG Research Unit The Jena Experiment (FOR 5000) · Duration: 2024–2028 · More: Subproject page