Risø-DTU willow field and tall mast RIWI (Super Site)


  • Coordinates: 55°41’31.95“ N, 12°6’14.69“ E
  • Height: 213 m
  • Base level: -2m ASL
  • Country: Denmark
  • InGOS observations: CH4, N2O, CO2
  • Responsible partner: Technical University of Denmark (DTU)
  • Responsible PI: Andreas Ibrom (anib@kt.dtu.dk)
  • TNA access: access request page
  • Website:


The willow-field (DK-RCW) is situated adjacent to the DTU-Risoe campus on DTU-owned land. It Comprises a 10 ha willow [Salix triandra x S. viminalis & Salix schwerinii x S. viminalis x S. vim.] energy crop plantation established in 2010 on fertile (loamy sand soil) agricultural land. The site was subject to slurry fertilization 150 kg N ha-1, (30 t digested slurry) upon planting in 2010. In winter 2012/13 the willow was cut and mineral fertilizer at 120 kg N ha-1 added in April. Analysis of N2O and CH4 fluxes were commenced in July 2010 by manual (n=24) and automatic (n=1) chambers. These analyses have been maintained at campaign basis.

A 12 m tall tower has been erected in the field in 2010 measuring air and soil temperatures, relative humidty, wind speed and direction (10 m), soil water contents in different depths, incoming and reflected short and long wave radiation as well as photon flux densities of photosynthetically active radiation (PAR, 400-700 nm). The phenological status of the willow plants and their light absorption can be estimated from above and below canopy PAR measurements and a web-cam producing one picture every 30 minutes in daylight hours. Biometrical parameters, the leaf area index (LAI) and soil respiration are being measured in regular campaigns.

Eddy covariance CO2 / H2O flux measurements were initiated at the site in July 2010. In august 2012 to august 2013 a N2O real-time analyzer (LGR Off-axis ICOS QCL) was applied for eddy covariance N2O-flux measurements. Additional activities comprise monitoring of soil environmental parameters and above- and belowground plant biomass production.The data are available to the project at the European Flux Data Base under the identifier DK-RCW.

In April 2013, an international N2O flux measurement campaign was carried out at the site. One objective of the campaign was to compare N2O fluxes using a number of different chamber systems differing in chamber design, detector type (ECD, Quantum Cascade Laser, Fourier Transform Infra Red spectroscopy), and calibration standard gasses. A second objective was to achieve N2O-flux measurements based on Eddy Covariance approaches by three different systems.

Part of the InGOS infrastructure is a 125m tall meteorological mast at the Risø Campus that is operational since 1958. A close by laboratory offers ample space, power and data connectivity for analysers. Tubes can be installed through tunnels from the lab to the tower to sample air from different levels. Meteorological sensors (wind speed, temperature, relative humidity, 3D turbulence data) are measured in 6 levels by the Wind Energy Department (DTU-Wind).

Since July 2014 N2O fluxes are being continuously measured at 96 m height with a LGR Off-axis ICOS QCL and a METEK USA-1 sonic anemometer. In autumn 2014 a fast response open-path methane sensor (LI-7700) and CO2 (LI-7500) sensor will additionally be installed. The flux footprint covers the Roskilde Fjord to the West and North, The City of Roskilde to the South and agricultural area to the West. Continuous high precision CO2/CH4/H2O concentrations measurements have been started in spring 2011 by application of a Piccaro CRDS CH4 analyzer. Air pollutants are being continuously measured by NERI (National Environmental Research Laboratory, Århus University).

In 2013, collaboration with AgriParisTech INRA started to model the N2O and CO2 fluxes from the surrounding agricultural fields including the willow plantation. Data on soils and management for this area have been collected to enable modelling of GHG fluxes, reactive N leaching, and plant growth. In collaboration with INRA and Århus University water samples have been taken and will be used for an independent estimate of the N2O fluxes from the fjord.

Infrastructure and facilities

Mains power and data connections are available both in the willow field and at the foot of the tall tower. Laboratory facilities are available for supplementary analysis on GHGs (GC-ECD) and their isotopic composition (d13C, d15N, d18O).

References for Risoe Willow field observations

  • Brümmer, C., et al. 2014. Gas chromatography vs. quantum cascade laser-based N2O flux measurements using a novel chamber design. Submitted
  • Carter, M.S. et al. 2014. Comparison of five chamber systems for N2O flux measurement based on a field campaign. In preparation.
  • Carter, M.S., Hauggaard-Nielsen, H., Heiske, S., Jensen, M., Thomsen, S.T., Schmidt, J.E., Johansen, A. and Ambus, P. 2012. Consequences of field N2O emissions for the environmental sustainability of plant-based biofuels produced within an organic farming system. Global Change Biology Bioenergy 4: 435-452.
  • Ibrom, A., Brümmer, C., Hensen, A., Asperen, H.V., Carter, M.S., Gasche, R., Famulari, D., Kutsch, W., Pilegaard, K. and Ambus, P. 2014 Eddy covariance N2O flux measurements at low flux rates: results from the InGOS campaign in a Danish willow field. EGU General Assembly 2014, Vienna.