About


Context

The Swiss FluxNet initiative combines ecosystem-​scale CO2 and H2O vapour (at some sites also CH4 and N2O) eddy-​covariance flux measurement sites in Switzerland. It currently encompasses seven long-​term ecosystem sites, six run by our group, covering the major land-​use types in Switzerland:

Flux measurements in an urban setting (Basel) as well as within a watershed (Rietholzbach) complement the Swiss FluxNet. Further sites with short-​term measurements such as Dischma (winter measurements over grassland; closed down) and Oensingen (grassland; closed down) provided additional information. Besides the Grassland Sciences Group, further research groups carry out flux measurements in Switzerland (see Partners on this page).

 

Approach

Ecosystem flux measurements of CO2, H2O vapour, CH4 and N2O are performed with the eddy covariance method. The eddy covariance method is based on high frequency measurements (10–20 Hz) of turbulent fluctuations in vertical wind velocity and the mixing ratio of a trace gas. The ecosystem flux itself is calculated from the covariance between these two measurements using time averaging of typically 30 min.

 

Technical specifications

  • Highest-quality infrared gas analyzers (CO2, H2Ov) and laser spectroscopy (CH4 and N2O) to resolve turbulent short-term fluctuations in the trace gas mixing ratio
  • Micrometeorology sensors: 3D sonic anemometer for wind speed and directions; radiation sensors, particularly for radiation balance
  • Soil climate profiles (temperature, moisture, soil heat flux)
  • Auxiliary instrumentation to measure variables such as soil CH4 and N2O fluxes, soil/stem/leaf respiration, xylem sap flow, phenology, leaf area index (LAI), biomass, precipitation, fog, etc.

 

Auxiliary measurements

An additional experiment started in summer 2016 at the Lägeren site: using tea bags to study decomposition in a highly standardized way. More information about the so-called Tea Bag Index can be found here or watch a short video.