The measurement of soil CO2 evolution in situ

Abstract

Three CO2 evolution measurement techniques were compared in a 28-year old slash pine plantation (Bradford Co., Florida, U.S.A.). Total forest floor CO2 evolution was estimated using a dynamic system with CO2 measured by an infrared gas analyzer (IRGA) system and two static techniques, one using granular soda lime and the other 1.0 N KOH. CO2 evolution measured with the IRGA system was not sensitive to variation of flow rates between 1 and 8 l min-1 (4-8 cm sec-1). Coefficients of variation were consistently higher with the dynamic system than with either of the static techniques. The IRGA method was compared with simultaneous soda lime measurrments over a six month period. Although there was no significant difference between winter IRGA and soda lime estimates at low CO2 evolution rates, the IRGA estimates increased to more than twice the highest soda lime rate during the summer. There was no signifieant difference between CO2 evolution rates measured with KOH or soda lime, and we suggest that divergence of dynamic and static methods is related to physical effects of moving air, rather than to the chemistry of the absorbent.