COMPARISON OF 2 STATIC CHAMBER TECHNIQUES FOR DETERMINING CARBON-DIOXIDE EFFLUX FROM FOREST SOILS

The similarity of two commonly used methods of measuring CO2 fluxes from forest soils was assessed by directly comparing the soda-lime method with a static chamber technique using gas chromatographic analysis of CO2 -concentration changes during short-term incubations. A paired-chamber sampling design was applied in 11 different forest stands to examine the two methods across a range of soil-CO2 efflux rates. Carbon dioxide efflux rates were highly variable within sites, and showed no spatial autocorrelation. No consistent differences in measured rates of CO2 efflux were observed between the two methods, indicating that either method may be applied to the range of mean daily rates encountered in this study (1.7-11.4 g m-2 d-1). A large number of chambers can be deployed with the soda-lime method, but no information on diel variations in efflux rates is obtained. The short-term incubation technique, on the other hand, can be utilized to simultaneously monitor several trace gases and diel trends in flux rates. Selection between the methods should be based on the hypotheses being tested or on practical constraints.