Automated soil CO2 efflux: Design and implementation in combination with whole ecosystem gas exchange in the EPA’s Teracosm Research Facility

One third of all terrestrial C is stored in soils and extensive research is underway to assess potential losses of belowground C under future warming scenarios.  Until recently, most measurements of soil CO₂ efflux were collected during daylight hours with total daily, seasonal and annual losses extrapolated across diel and seasonal temperature changes.  Individual laboratories have built automated chambers to obtain continuous monitoring of soil CO₂ efflux and LiCor has recently marketed an automated soil CO₂ efflux system.  Unfortunately, these systems are generally designed for field sampling and their large size can be prohibitive for use in smaller closed-chamber or mesocosm studies often used for climate change research.  Here, we show the design and implementation of a small-scale (15cm diameter) automated soil CO₂ efflux chamber designed to work in combination with whole ecosystem gas exchange measurements in the EPA’s global climate change research facility.  Our chamber is supported by a frame that attaches directly to the soil collar and is operated by a pneumatic cylinder that raises the chamber vertically.  For three minutes of each hour, the IRGA used for monitoring whole ecosystem gas exchange is diverted to measure soil efflux.  The simple, low-cost design of our chamber is easily replicated, and preliminary results show no difference when compared with the LiCor 6200.  The design of this smaller-scale automated soil CO₂ efflux system may be useful for measurement of respiratory C losses for closed chamber or mesocosm studies where space is a limiting factor.