Carbon dioxide efflux from the floor of a boreal aspen forest. II. Evaluation of methods — verification by infra-red analysis of a dynamic closed chamber

Abstract

Concern over the global exchange of carbon has highlighted the need for reliable estimates of soil CO2 efflux (soil Fc). Appropriate methods to estimate soil Fc must be identified and adopted. In this study we used a dynamic closed chamber and infra-red gas analyzer (DCC-IRGA) to verify the use of three other methods in a boreal aspen (Populus tremuloides) forest. The three methods were: (1) soil CO2 concentration gradients and volumetric soil moisture by both diffusion theory (a) and empirical relationship (b), (2) an automated steady-state chamber and (3) daytime estimates derived from a relationship between soil temperature and nighttime eddy correlation measures of CO2 fluxes above the forest understory (4 m) and overstorey (39 m). We found reasonable agreement between DCC-IRGA and method 1a (R2 = 0.44 to 0.62), and excellent agreement between DCC-IRGA and the other methods (1b, R2 = 0.76 to 0.88; 2, R2 = 0.89 and 3, R2 = 0.64 to 0.80). Each of these methods has advantages beyond the scope of the DCC-IRGA, and these are discussed. Key words: CO2 flux, soil respiration, soil CO2 concentration, eddy correlation