Setup & Design

Dimensions & Segmentation

EcoUnits are experimental chambers comprising a bottom part (‘belowground part’), an upper part (‘aboveground part’), and a technical part on the top.

The upper part is equipped with lighting, ventilation, and irrigation installations as well as the control cabinet.

The aboveground part provides sufficient space for the growth of herbaceous plants and tree saplings and creates the preconditions for developing complex interaction networks of plants and a wide range of invertebrates.

The belowground part can be filled with up to 1.23 m³ of soil or alternatively can be equipped with four steel cylinders (lysimeters of 0.5 m in diameter) each holding 0.16 m³ of soil.

The EcoUnits can be divided into four belowground compartments using the lysimeters and into four equally sized aboveground segments using mobile interior walls. Each EcoUnit can thus be separated above- or belowground, or both, creating four separated chambers between which organisms and materials cannot exchange. Each quarter has its own lighting, irrigation, and ventilation system as well as permanent measurement equipment. In this way, up to four different treatments can be implemented in each EcoUnit. With the lysimeters, it is possible to excavate intact soil monoliths directly from the field, which then provide a natural, undisturbed ecosystem for belowground organisms.

Permanent Installations For Continuous Monitoring

In both the aboveground and belowground part, there are four sensors each for measuring air/soil temperature and humidity. Further, tensiometers can measure soil moisture tension in three different soil depths. All data is automatically and continuously transmitted to a database. Suction probes at the bottom of the soil container or the lysimeters continuously collect pore water for chemical analyses. Four HD-IP video cameras in the aboveground part can monitor vegetation development or insect behavior, such as movement and habitat use. Several openings in the walls of the lower part allow horizontal soil samplings or the installation of acrylic glass tubes to monitor root development using a portable root scanner^[1].

Reference
[1] Möller, B., Chen, H., Schmidt, T., et al. and Posch, S. (accepted manuscript) rhizoTrak: A new software tool for manual annotation of time-series images from minirhizotrons. Plant and Soil

Environmental Conditions

The environmental conditions in the EcoUnits (lighting, irrigation, and ventilation) are remote-controlled via a network and logged in the database.

Light:
Each EcoUnit has four LED lamps with four color (wavelength) channels. Each of these wavelengths can be individually set to intensities from 0 to 100 %, allowing variation in the composition of the light spectrum (e.g., a higher proportion of red light at dawn and dusk). The available color channels are white (3000 K and 5000 K), ultraviolet (400 - 405 nm), blue (460 - 475 nm), and
red (625 - 720 nm).

Irrigation:
Four irrigation nozzles installed at the top of the upper part allow automated and evenly distributed irrigation with deionized water, controlling the flow rate (by changing the water pressure), the amount of water, and the frequency of irrigation events. All four quarters of the chamber can be irrigated individually.

Climate:
Temperature and humidity are controlled centrally in the iDiv Ecotron hall. The ventilation can be set to automatically adapt the climatic conditions inside the EcoUnits to the conditions in the hall by increasing or decreasing the fan speed. All four quarters of the chamber can be regulated individually.

Soil temperature:
To simulate a natural soil temperature gradient (often decreasing with increasing depth), a capillary system with circulating coolant is implemented at the base of the soil container. The soil temperature can be controlled per EcoUnit.

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