The international development of ecotrons for experimental ecosystem studies

A research review on “Ecotrons: powerful and versatile ecosystem analysers for ecology, agronomy and environmental science”, has been recently accepted in Global Change Biology, underlining the features of ecotrons in ecosystem science.
 
An ecotron is “an experimental facility comprising a set of replicated enclosures designed to host ecosystems samples, enabling realistic simulations of above and belowground environmental conditions, while simultaneously and automatically measuring ecosystem processes”. They are prominent for their capacity to simulate and measure multiple environmental conditions and their focus on non-destructive, automatic, real-time measurements of ecosystem-level processes. About a dozen of these new, large facilities are operational around the world.
 
What distinguish ecotrons from Controlled Environmental Facilities (CEF) is their capacity to improve realism, defined “as providing conditions as close as possible to the complexity of natural environments, whether in the past, present or predicted future”. In order to get closer to realistic outdoor conditions, ecotrons needs to incorporate above and belowground biological complexity and spatial heterogeneity. This is made possible by using large ecosystem samples hosted in large enclosed atmospheric volumes. Some ecotrons also take advantage of natural sunlight.
 
Ecotrons are also remarkable by their significant experimental flexibility. Different types of treatments can be hosted (climate, atmospheric composition and pressure, pollution, soil types…) and there is a possibility to change the targeted model system from one experiment to the other which allow ecotrons to cover a wide range of ecosystems (grasslands, peatlands, forests, agricultural systems…). The dimensions (i.e., size of the tanks, height of the canopy enclosures) are adjustable and the ecotrons air circuits also allow to temporarily install supplementary costly instruments, such as volatile organic compound (VOC) or NOx gases analysers.
 
Ecotrons are complementary to field and laboratory experiments. Indeed, they are really interesting for “hypotheses that require environmental conditions technically difficult to achieve in the field and/or intensive process measurements, as long as the number of drivers remains low.”
 
Major scientific achievements have been made already mainly in 1) ecosystem response to abiotic global change drivers (55% of the papers), 2) ecosystem processes (27%) and 3) biodiversity–ecosystem functioning relationships (18%).
 
Areas of improvements for ecotrons are suggested such as testing and deploying additional alarms taking into account correlation between replicates and between parameters in order to early detect sensor malfunction or deviation from target climatic conditions. More research could be made regarding the soil functioning, for example from non-invasive soil process measurements via automatic gas sampling in the soil, or comprehensive soil VOCs chemotyping. It is also highlighted that modelling should take a more prominent place in ecotron experiments in order to better manage the experiments and improve predictions of ecosystems states during the course of experiments.
 
The paper can be downloaded freely here