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Automated chamber techniques

arable lands

Both static and dynamic chamber techniques can be coupled with automatic gas sampling and analysis systems, resulting in automated chamber systems. Environmental parameters (e.g. soil and air temperature, soil moisture) are monitored simultaneously. Thus, automated chamber systems are powerful tools for the in situ investigation of soil-atmosphere trace gas exchange and its response to changes in the environmental conditions. Furthermore, since monitoring takes place quasi continuously (several measurement a day), these systems permits accurate surveillance of temporal dynamics of trace gas emissions and reliable detection of short-lasting events which may be missed with manual sampling methods.
In the automated chamber systems developed at IMK-IFU, the whole system is controlled by sampling and recording units using data logging modules and relays. The main components of such systems are chamber blocks, control unit, gas analyzers and environmental monitoring unit.
One chamber block is closed and opened simultaneously with pressurized air applied to the lids, and gas samples are taken sequentially from all chambers. Within each measurement cycle, this procedure is repeated once per chamber block of the system. Chambers closing period and gas sampling temporal sequence -as well as size and shape of the chambers- depend on the investigated ecosystem and the trace gases of interest. By means of a control unit, gas samples are sent to the gas analyzer units, in order to determine the concentrations of the trace gases. Gas chromatographs (ECD and FID detectors) and IRGA probes or quantum cascade lasers (Aerodyne) are used to investigate N2O, CH4 and CO2. In the case of NOx and O3, chemiluminescence detectors are used. Parallel, a sort of probes measures continuously environmental parameters -e.g. soil temperature, soil moisture at different soil depths and precipitation-. Data are stored by data logging modules; besides the importance of the ancillary data for interpretation of results and environmental monitoring, this information can act as an alarm to stop the monitoring (e.g. opening of chambers in case of precipitation or too high temperatures).

The Höglwald-Forest long term observatory (since late 1993) with fully automated chambers systems for continuous year round flux measurements of N2O, CH4, CO2 and NO.

Automated chamber systems are operated at permanent experimental sites (ICON, Höglwald, TERENO). In addition, our research division uses several mobile systems which can be deployed at various field sites. These mobile systems have e.g. been used for soil trace gas exchange in tropical forests, savanna, poplar plantations, grassland, arable systems etc. across the globe.
Contact persons: Georg Willibald, Rainer Gasche, Ralf Kiese, Klaus Butterbach-Bahl.

Robotized system

'Light' chamber for automated NEE and ER measurements
Combined robot and lysimiters systems for capturing ecosystem matter fluxes at Rottenbuch grassland field.

At the TERENO grassland sites Fendt and Rottenbuch, robotized static chamber system have been deployed which allows automated continuous measurements of soil/atmosphere exchange of N2O, CH4 and CO2 in high temporal resolution. For this a measuring chamber (1 meter diameter, variable height according to vegetation development state) is sequentially moved from one lysimeter position to the next, while during closure times (< 20 minutes) the change in headspace gas concentrations is measured automatically and in high precision with a quantum cascade laser (Aerodyne). Changes in gas concentrations with time is finally used for calculation of fluxes. At the field site Fendt a "light" chamber is installed allowing measurements of both net ecosystem exchange (NEE, with light) as well as ecosystem respiration (ER, in the dark ) in automated mode in high temporal resolution.
Contact persons: Ralf Kiese, Rainer Gasche, Anne Schucknecht, Georg Willibald, Klaus Butterbach-Bahl.

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