A multichannel automated chamber system for continuous measurement of forest soil CO2 efflux

Development of a fast-response multi-chamber system for measuring soil-surface carbon dioxide efflux is described. The sixteen-chamber automated system continuously monitors surface carbon dioxide efflux at different locations within a forest ecosystem using a single infrared gas analyzer that successively measures gas samples from each of the sixteen chambers. The chambers have lids that open and close automatically, and are connected in parallel to the single carbon dioxide analyzer which is equipped with a sixteen-channel gas sampler. Air is withdrawn continuously from the inlets and outlets of each chamber and fed sequentially to the gas analyzer. Using this instrument, surface carbon dioxide efflux was measured in a 40-year old pine forest during a three-month period (February to May) in 2001. Results showed a steady increase in mean carbon dioxide efflux during the period. A statistically significant correlation between soil-surface carbon dioxide efflux and surface temperature was also established. Spatial variation of carbon dioxide efflux was found to be higher in the non-growing season than in the growing season. It was concluded that the multi-channel automated chamber system can provide large amounts of high quality data on soil carbon dioxide efflux over a large surface area and simultaneously evaluate both spatial and temporal variation. The system uses a relatively small amount of power (70 W maximum) which can be further reduced (to 15 W) by minimizing the pressure difference between inside and outside the chamber. The system requires no maintenance other than the calibration of the gas analyzer and measurement of the flow rate through the chambers. 34 refs., 8 figs