BioCliVE allows to precisely construct future grassland ecosystems and thus to demonstrate causal inter-relationships between biodiversity, climate change and functioning. However, despite being as close as possible to natural grasslands, it is a constructed artificial system. We will thus validate our results by comparing our data with a similar climate change experiment that we set up in a semi-natural grassland. With these two experiments we will advance our understanding of ecosystem resistance and resilience to extreme climate events.
In 2015, we established a new climate change experiment at Fort Rhijnauwen manipulating a major driver of change within grassland - drought. We exclude rainfall with rainout shelters such that precipitation is reduced by a constant percentage. This experiment will contribute to the Drought-Net International Drought Experiment that uses standardized methods to simulate drought and therefore allows comparison of ecosystem responses worldwide.
The experiment consists of four treatments replicated in a randomized block design, with three blocks of four plots for a total of 12 plots. The four treatments are:
- Reduced annual precipitation: This treatment simulates a reduction of precipitation throughout the year corresponding to the lowest yearly amount of precipitation received during the last 60 years of local precipitation records. At our site this correspond to 50% reduction of rainfall year-round.
- Seasonal shift in precipitation. This treatment simulates a change in precipitation pattern throughout the year with wetter winters and dryer summers. Dryer summers consist of 90% reduction of rainfall in the summer months (June, July and August) of each year and wetter winters consist of adding the amount of precipitation that was removed in summer during the winter months (November to March).
- Infrastructure control: This treatment allows us to account for the side effects created by the structure of the shelters (e.g. heat, moisture, light).
- Ambient control: This is the unsheltered control receiving ambient precipitation.
Plots have been hydrologically isolated by trenching to a depth of 50 cm along the border of each shelter and control plots.
Each year, we measure the impact of drought on plant diversity, on the cycle of carbon and on the stability of biomass production.