The added value of ecotrons
The UHasselt ecotron facility lies in the middle of this range of complementary approaches.
An ecotron is a large-scale research infrastructure that allows to expose large ecosystem samples (“mesocosms”) to highly controlled climate conditions, and monitor their response at a high frequency.
The large size of the mesocosm (usually the equivalent of a pot weighing several tons) and the high number of climate parameters controlled allows for a good blend of control capacity and realism. Only a few ecotron facilities exist in the world, because they are extremely complex to design. With such tool, one can estimate how climate change will affect ecosystems at the meter scale. Scaling up to the landscape, however, requires complementary field experiments and modelling, while understanding the impact on separate species or specific mechanisms can be achieved with laboratory or growth chamber experiments.
The UHasselt Ecotron facility is made of 12 separate units. Each one consists of three compartments: a dome (1), a lysimeter (2), and a chamber (3).
1) The dome consists of a shell-shaped dome made material that is transparent to the part of the light spectrum used by the plants for photosynthesis (Photosynthetically Active Radiation: PAR). There, wind is simulated using fans and precipitation using a water nozzle. Additionally, we measure the air temperature, the air relative humidity, concentration of greenhouse gases (CO2, N2O, CH4), the amount of energy entering the mesocosm (photosynthetic photon flux density: PPFD), and the PAR.
2) The lysimeter is a steel cylinder containing the mesocosm and designed to measure the movements of water inside. Each lysimeter is equipped with sensors measuring soil temperature, water content, water tension (force necessary for plant roots to extract water from the soil), and soil electrical conductivity (amount of salts in soil); all of these sensors are present at 5 depths (10, 20, 35, 60, 140cm) and at 3 different horizontal positions for each depth. Suction cups are sampling soil water according to the same 5x3 design. These lysimeters are also equipped to control soil temperature (through a heat exchanger) and soil water tension (through a suction/injection system), to reproduce field conditions, where soil is colder and wetter with depth. The lysimeter and the water leaching through it are also measured every minute; this allows to calculate water budgets.
3) The chamber is the gastight room that encloses the lysimeter. There, we control air temperature (with two large heat exchangers), relative humidity (with a mist generator and an air dessicator), and CO2 concentration (with a CO2 injection system and a CO2 scrubbing box).
The UHasselt Ecotron is linked with a nearby Integrated Carbon Observation System (ICOS) ecosystem tower, which provides real-time data on local weather and soil conditions, with a frequency of at least 30 minutes. However currently many chambers are following the climate model outputs (collaboration with VUB).
The design of this infrastructure benefited from exchanges through the AnaEE (Analysis and Experimentation on Ecosystems, )/ESFRI (European Strategy Forum on Research Infrastructure) project. Some of the infrastructure’s features were inspired by the ecotron platform of the CNRS Montpellier Ecotron.
The system enables long- and short -term simulations to study ecosystem functioning and ecosystem dynamics in natural and agricultural ecosystems. Currently two large projects are running in the facility. An international, interdisciplinary research consortium is investigating the effect of climate change on the ecosystem services provided by a dry heathland ecosystem. A second experiment is focusing on growing food crops on marginal lands in the future (BioFoodonMars, FACCE 2020).
Extra access to the Ecotron Hasselt University is therefore currently restricted to researchers that would investigate hypotheses complementing, but not interfering the ongoing two projects. However, new project proposals for the future (from 2021 onwards) are welcomed and will be screened by the AnaEE Flanders commission.
To enhance the interdisciplinary research opportunities and to accommodate (part of) its research and its researchers the Centre of Environmental Sciences has established a Field Research Centre (FRC) on the main entrance to the national park Hoge Kempen (NPHK). The FRC - UHasselt is responsible for the daily management of the Ecotron.
The Centre of Environmental Sciences (CMK-UHasselt) and the Plant and Vegetation Research group (PLECO-UAntwerp) combine - together with the Sphere-group (UAntwerp) - their expertise in the Centre of Excellence ECO. To enhance their expertise state-of-the-art research infrastructure is being built. The ecosystem measuring tower is one infrastructure, the Ecotron Hasselt University is another important ambitious infrastructure.