As part of the GREENHOUSE project, a one month long field campaign was conducted to gather information on spatial and temporal patterns of greenhouse gas fluxes from arable farmed land. This campaign was carried out on a rapeseed crop site, located in Lincolnshire, from March to the beginning of May 2014. The principal participants were the Centre of Ecology and Hydrology (Wallingford, Edinburgh and Lancaster), the University of York and the University of Edinburgh.

Static chamber measurements for monitoring photosynthetic responses to variable light conditions. This image shows a black translucent sheet covering the gas chamber that acts to diffuse the solar irradiance.
Top: The Skyline system for automated greenhouse gas chamber measurements installed within the site. Bottom: View of the Perspex Skyline chamber and boardwalk along the automated track. Collars where chamber measurements occur can be seen in the image as white rings.

Routine measurements of CO2, CH4 and N2O fluxes during the campaign were principally conducted at a series of 16 ground collars located in the fetch of two eddy-covariance towers (see the fieldsite map below) and another series of 18 ground collars that were part of University of York’s Skyline system, shown in the images on the right and described in more detail below. Ancillary measurements included soil moisture and temperature and canopy height and density along with leaf and soil samples that were collected for further analysis. Additionally, to understand the impacts of variable solar radiation on gas exchanges associated with canopy-scale photosynthesis, a series of manual light response experiments was conducted by the University of Edinburgh. Light response measurements involved placing a clear chamber over the vegetation within a collar using, where necessary, a cylindrical extension to ensure that the chamber covered the upper canopy without damaging the crop. With the vegetation enclosed, a Licor 6400 instrument monitored the change in CO2 gas concentrations inside the chamber over a one minute time period. The process was repeated using a series of partially opaque sheets to cover the chamber to gradually reduce light levels inside the chamber therefore simulating alterations in sky conditions. Between each measurement the chamber was lifted to allow conditions inside the enclosure to return to normal.

One of the most predominant features located on the Lincolnshire field site was the novel Skyline gantry system (right) - installed and managed by The University of York. The Skyline system is used for collecting automated chamber measurements of CO2, CH4 and N2O fluxes throughout each day from 18 ground collars. Sensors buried along the length of the gantry are also used to monitor soil temperature and moisture to resolve fine-scale variations in soil parameters.

Additional features installed at the field site include mobile eddy-covariance towers maintained by the Centre for Ecology and Hydrology (CEH). The towers provide near-continuous observations of CO2 and N2O at the field (~1 ha) scale.

Map of the Lincolnshire field site. Digitised features - crop area, tram lines, locations of collars and survey equipment- were derived from GPS surveys conducted by Emanuel Blei and José Parejo.