�����̨

Researchers at Utrecht University are mapping the effects of biodiversity and climate change on grassland functioning on a daily basis. In hundreds of containers behind the greenhouses of the Botanic Gardens, plant and soil ecologists from the Ecology and Biodiversity Research Group create future natural grasslands. In Dutch grasslands, biodiversity is being lost at incredible rates. But biodiversity keeps grasslands resilient as the climate changes. Future grasslands need biodiversity to continue producing biomass, storing carbon, and cycling nutrients in a stressful climate. The Biodiversity and Climate Variability Experiment (BioCliVE) at Utecht University manipulates these factors at a unique scale.

Ecosystem of the future

Currently, biodiversity is under pressure, and the climate is becoming more extreme and more unpredictable with higher temperatures and more floods and droughts. Biodiversity forms a natural protection against the effects of climate change, a kind of natural insurance, but biodiversity is also being lost. For example, research has shown that communities with multiple species contain many different types of drought tolerance and so are able to survive when monocultures cannot. However, as we lose biodiversity due to anthropogenic activities, we lose this insurance.

At the BioCliVE, researchers investigate the processes by which plant diversity ensures grassland functioning despite future changes in precipitation patterns. Specifically, they want to understand the factors that make grassland communities more resistant to extreme events and enable them to recover better after such events. By gaining a deeper understanding of these processes, the researchers are better equipped to comprehend how these ecosystems function and to develop strategies for restoring degraded ecosystems.

Manipulating the climate

The experiment consists of 352 containers, each containing roughly 1,000 liters of soil taken from a natural riverine grassland. Some containers contain one or four plant species, others eight or twelve.
The containers each have their own watering system so that researchers can precisely manipulate the climate: some containers face wetter winters and drier summers, others more extreme weather events, and some received a combination of both. The team started examining the resistance of the plant communities to an experimentally imposed extreme drought event, which lasted for two months in 2023. After the drought, precipitation returned to normal to assess the recovery of the ecosystems.

The next step is to impose an extreme flood event to investigate the effects of this additional stressor. Before proceeding with this manipulation, researcher want to determine whether the grasslands have recovered to their pre-drought state, as they were in early 2023. This will be explored in the coming year. This allows understanding the processes by which grasslands can resist and recover from extreme weather events. However, it remains uncertain whether full recovery is achievable.

Effect on each other plants

Plant species influence each other. For instance, some species provide shade to others, while those with long roots ensure that water reaches the topsoil, allowing plants with shorter roots to access water. To properly measure these effects, mircoclimate sensors have been established in all 352 containers.

In the coming years, researchers will continue to study the characteristics of plant communities at the BioCliVE. This will allow them to determine even more precisely how climate change is impacting grassland functioning. They examine factors like the size of the leaves, or the length of the roots. By mapping these characteristics, researchers aim to enhance the resilience of grasslands in the future.

This knowledge can be applied not only in the Netherlands but also in other countries with similar climates. “The BioCliVE is really such a unique set up to understand how plants are interacting. Plants behave differently when they are stressed, and we can be so much more precise with how we stress our plants out at the BioCliVE! Understanding these interactions will make it possible for us to work with restoration practitioners and land managers to help meet goals that are focused on the community’s resilience to stress and how well they function instead of comparing them to references that are changing all the time.” says Kathryn Barry who coordinates the daily operations of the BioCliVE.

Already a success

“We are very curious about the results in the coming years, but above all, we are already very proud of what we have achieved so far. For us, the experiment is actually already a success. It has greatly contributed to the visibility of the university and the faculty. Additionally, BioCliVE provides a structure for education and long-term training for students at different levels. Already 50 students have contributed to the experiment.” Says Yann Hautier, Scientific communications manager and co-coordinator of the BioCliVE.

“In addition, we hope to publish the first interesting research results in the coming year, which is promising for the future.”

Time and money

Setting up the experiment took a considerable amount of time. First, the ecosystems had to be created in all the containers. Only once these were established could the precipitation treatment officially be implemented. Alongside the establishment, funding was required to construct a large retractable roof greenhouse over the experiment. This greenhouse covered all the plots, enabling the researchers to manipulate precipitation through a drip irrigation system.

Given the long duration of the experiment, traditional funding schemes, which typically focus on short-term projects, were not suitable. To address this challenge, funding was raised from various sources. This included contributions from the Ecology and Biodiversity group and the Department of Biology, but most notably, the Utrecht University Fund which was able to engage more than 500 donors, along with several trusts and foundations, to provide financial support for the project.