The iDiv Ecotron
Biodiversity-ecosystem functioning research under controlled environmental conditions
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The Ecotron is a joint research platform from iDiv and the Helmholtz Centre for Environmental Research – UFZ. It is an indoor research facility housing a set of 24 identical experimental units, called EcoUnits, each of which will harbour one to four isolated ecosystems confined in compartments. Species assemblages within ecosystems can be manipulated above and below the ground, varying horizontal diversity (i.e. the number of species within a trophic level) and vertical diversity (i.e. the number of trophic levels). Ecological processes in the Ecotron can be measured with non-invasive methods, while environmental conditions are either controlled for the whole set of replicates (air temperature) or for each replicate individually (e.g. irrigation, illumination, soil temperature).
Recent research highlights that diversity at higher trophic levels (e.g. aboveground herbivores and predators and belowground herbivores, predators and decomposers) can simultaneously influence multiple ecosystem functions (= multifunctionality)1,2. These higher trophic levels, however, are often strongly negatively affected by anthropogenic pressures such as land-use intensification3,4. Research in the Ecotron will focus on understanding relationships between horizontal (i.e. the number of species within a trophic level) and vertical biodiversity (i.e. the number of trophic levels) and ecosystem functioning, particularly taking higher trophic levels into account. Three key questions we want to address are:
- Does complexity of species interaction networks influence ecosystem functioning?
- How are ecosystem functions depending on the connections between aboveground and belowground organisms and processes?
- What is the impact of global change on biodiversity, interaction networks and ecosystem functions?
We will use the wide range of experiences, approaches and expertise of the scientific community within iDiv to implement multiple sub-studies within the broader long-term experiments, dealing with different taxonomic or functional groups of organisms and different ecosystem functions and processes. Synthesis of these findings will enable us to gain a holistic understanding of the ecosystems studied and to generalize the mechanisms of how various components of biodiversity contribute to ecosystem multifunctionality.
To address our research questions we will manipulate the diversity within and between trophic levels and functional groups and set up treatments with different global change scenarios. Ecotron experimental units (EcoUnits) are designed to support a broad range of growth forms and life strategies allowing us to investigate the interactions among primary producers, decomposers, herbivores, predators, mutualists, parasites and pathogens as well as abiotic conditions. Plants, such as bryophytes, herbs, shrubs and tree saplings, will be grown in EcoUnits. Aboveground animals (e.g. insects, spiders and molluscs), belowground animals (e.g. insects, earthworms, springtails, mites and nematodes) and microorganisms (bacteria and fungi) will be introduced. Abiotic conditions including light intensity, irrigation, nutrient supply, or toxins will be manipulated. We will monitor a number of parameters with non-invasive methods using permanently installed measurement equipment, automated soil water sampling and video cameras (see EcoUnits).
To develop experiments and to organize collaborations in the Ecotron project, we established an Ecotron Scientific Committee dealing with all scientific and administrative issues related to the research platform. The members of the Committee are Nico Eisenhauer (iDiv/UL), Ulrich Brose (iDiv/FSU), Alexandra Weigelt (UL), François Buscot (UFZ/UL), Stan Harpole (iDiv/UFZ/MLU), Martin Schädler (UFZ) and the Ecotron Coordinator Manfred Türke (iDiv/UL).
1 Lefcheck et al. (2015) Nature Comm. 6: 6936
2 Soliveres et al. (2016) Phil. Trans. R. Soc. B 371: 20150269
3 Allan et al. (2014) PNAS 111: 308–313
4 Attwood et al. (2008) Global Ecol. Biogeogr. 17: 585–599
Launch of the Ecotron
The Ecotron is currently under construction and will be ready to host its first experiment in autumn 2016. It will be implemented in a climate-controlled hall on an area of 580 m2, located within the research station of the Helmholtz Centre for Environmental Research - UFZ in Bad Lauchstädt (Saxony-Anhalt). The research station offers a great infrastructure to support Ecotron research in terms of laboratory space and equipment, greenhouses, and machinery for soil processing.
EcoUnit / Ecotron prototype
The prototype of an experimental unit, the EcoUnit, was built and delivered to the Helmholtz-Centre for Environmental Research UFZ in Leipzig in July 2015. In the subsequent months, we evaluated the prototype experimentally, assessing light intensity, heterogeneity and spectra, irrigation heterogeneity according to different types of nozzles, ventilation and air flow and other aspects. We used the results of these tests to improve the design of the final EcoUnits. Finally, the prototype will be modified to become one of the 24 EcoUnits.
EcoUnits are experimental chambers with the total dimensions of 1.55 × 1.55 × 3.20 m (L × W × H), comprising a lower part, which is filled with soil (belowground part), an upper part (aboveground part) and a technical section on the top. The frame of the chamber is constructed of aluminium profiles providing stability and flexibility as additional components can easily be added at any time.
The lower part includes a container with the inner dimensions of 1.24 × 1.24 × 0.80 m (L × W × H), which may be filled with 1.23 m3 of soil (≈ 2.2 t) or alternatively may hold four steel cylinders (lysimeters) of 0.50 × 0.80 m (D × H), each containing 0.16 m3 of soil (≈ 0.28 t). Lysimeters may either be filled with soil by hand or may be used to excavate intact soil monoliths from the field, which will then be transferred into the EcoUnit. Containers filled with soil as well as lysimeters provide a habitat size suitable for the establishment and the study of belowground organismic networks and processes.
The upper part has the inner dimensions of 1.46 × 1.46 × 1.50 m (L × W × H) providing enough space for even tall herbs and tree saplings to grow and for the development of complex interaction networks.
A technical section is placed on top of the upper part with installations for lighting, ventilation and irrigation as well as the control cabinet.
Each EcoUnit can be separated into four belowground compartments by using the four lysimeters and into four aboveground compartments of equal size by the installation of inner walls. Segmentation can either be done only below or only above the ground or in both parts together, creating four isolated spheres within one EcoUnit, where the exchange of organisms and materials among compartments is restricted. Each quarter of the chamber has its own lighting, irrigation and ventilation system as well as permanent measurement instrumentation. In this way, up to four different treatments can be applied in each EcoUnit.
Permanent installations for measurement instrumentation
In the aboveground part, there are four sensors measuring air temperature and humidity. In the belowground part, there are four sensors for the measurement of soil temperature and moisture as well as four tensiometers for measuring soil moisture tension in each of three different increments of soil depth (centre of sensor at 9.5, 21.5 and 43.5 cm soil depth). Data of these loggers is gathered automatically by the central control unit at chosen intervals. In the bottom of the soil container or on each of the four lysimeter compartments, there are suction probes continuously collecting pore water for chemical analyses. In the aboveground part, there are also four HD-IP-video cameras installed to monitor vegetation development over time and insect behaviour, such as movement and habitat use, herbivory, predation and pollination. Cameras can be used in darkness by using infrared light provided by the EcoUnit lighting.
In the walls of the lower part, there are four openings in each of the three increments of soil depth (one opening per increment in each lysimeter), which may either be used to take soil or soil volatile samples horizontally during experiments or for the installation of acrylic glass tubes inserted into the soil to monitor root development with the help of a transportable root scanner.
Each EcoUnit has a local terminal (touch panel) to set and control the parameters for environmental conditions and to define the logging intervals for data-loggers, which, however, can also be set for the whole set of 24 units, subsets of units, or individual units by the central control unit via the network. All settings for environmental conditions (e.g. changes in light intensity or irrigation events) are logged as well.
Light: Each EcoUnit has four LED lamps which are operated together. There are four colour (wavelength) channels, which can be set to intensities ranging from 0 to 100% individually. For each colour channel, the intensity can be defined for each hour over the course of the day and intensity will change gradually between subsequent hours with different settings. In this way, the relative proportion of light with different wavelengths can be modified within the light spectrum (e.g. a higher proportion of red light during dusk and dawn). The colour channels available are white (3000 K and 5000 K), UV (400 - 405 nm), blue (460 - 475 nm) and red (625 – 720 nm). At the maximum light intensity settings, PAR (photosynthetic active radiation) intensity at ground level will be >400 μmol s-1 m-2. It is possible to define a total light intensity level for all colour channels treated together between 0 and 100% for each day over the course of the year to simulate seasonal changes in light intensity and day length.
Irrigation: Four irrigation nozzles installed on the top of the upper part provide automated irrigation with deionized water, where flow rate (via modifications in water pressure), the amount of water and the frequency of irrigation events can be selected. Nozzles were chosen to achieve the best spatial homogeneity in precipitation on the ground area. Different irrigation schemes can be applied for the four quarters of the unit.
Climate: Temperature and humidity is maintained within the Ecotron hall. Information on temperature and humidity within EcoUnits, provided by the aboveground data-loggers, is compared to the conditions in the Ecotron hall and ventilation can be set to automatically adjust climate conditions within units to the conditions in the hall by increasing or decreasing fan speed. Manual settings can also be applied. Different settings can be applied for the four quarters of the unit.
Soil temperature: To achieve a near-natural soil temperature gradient with temperature increasing from deeper soil depths to the surface, a capillary system circulating a cooling medium was implemented in the bottom of the lower part/ soil container. Different settings using the data from the aboveground and belowground temperature sensors can be used to automatically adjust soil temperature. Soil temperature regulation can be done for each EcoUnit individually.
Prof. Nico Eisenhauer
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Dr Anja Schmidt
Position in Ecotron project:
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Research, collaborations, administration, contents, state of the art
+49 341 9733193
Position in Ecotron project:
Reasons for contact:
+49 341 9733191
Advantages to Lab and Field Studies
Results from lab experiments may not always reflect findings in natural habitats as the simplified settings in the laboratory may lack interactions among species and interrelations among ecosystem processes. On the other hand, in natural ecosystems environmental conditions vary greatly in space and time, and a wealth of (often unknown) factors influences ecosystem processes, causing variance in data, which may conceal or confound the general mechanisms behind the processes studied. The Ecotron allows for the construction of complex ecosystems resembling near-natural conditions but with the possibility to eliminate or reduce the variance from unknown factors (e.g. by controlling environmental conditions) and to easily measure most of the variables influencing ecological processes. Further, the Ecotron offers the opportunity to study ecological interactions of plants and invertebrates at appropriate spatial scales. Thus, the Ecotron will enable us to more comprehensively study the mechanisms underlying the relationship between biodiversity and ecosystem functioning.