Cranfield's Wolfson field laboratory is used for measuring whole-soil carbon balances and greenhouse gas fluxes, including stable-isotope compositions, in large, intact, hydrologically-isolated soil monoliths (lysimeters) under field conditions.
The laboratory contains 24 lysimeters connected to automated gas flux chambers and instruments. The lysimeters are 0.8m in diameter and 1m deep, i.e. at least the size of a soil pedon, and therefore representative of field soil conditions. Each is equipped with systems for controlling soil moisture and surface temperature, and instruments to allow near-continuous sampling of gases emitted from the surface, dissolved solutes passing out of the bottom, and temperature, moisture and soil solution at different depths. Onsite environmental conditions are monitored with a weather station.
About the facility
The gas flux chambers (26cm head space) are fixed over the soil surface and have pneumatically-operated lids. Gases accumulated in the head space when the lids are closed are passed through a continuous loop to a Picarro isotope analyser and an isotope ratio mass spectrometer housed in an instrument building. This allows simultaneous analysis of CO2, CH4, N2O, O2 and N2 and their C, O and N isotope compositions at natural or enriched abundances.
The soil monoliths in the lysimeters have automated sprinkler irrigation systems, delivering rainwater collected from the roof of the instrument building. At present, the system contains two soil types planted with grass. These are a well-drained, acid, coarse loamy soil from Bedfordshire, and a poorly-drained, seasonally waterlogged loamy soil over clay from Warwickshire. The soil monoliths were taken intact from these sites, preserving the natural soil structure, and brought to Cranfield.
Summary of applications
- The facility is used to measure whole-soil carbon balances and greenhouse gas fluxes in large, intact, hydrologically-isolated soil monoliths. The layout provides for multiple soil types and moisture and temperature regimes with statistically-robust replication.