Effect of carbon dioxide concentration on microbial respiration in soil

Abstract

Abstract In order to assess the validity of conventional methods for measuring CO 2 flux from soil, the relationship between soil microbial respiration and ambient CO 2 concentration was studied using an open‐flow infra‐red gas analyser (IRGA) method. Andosol from an upland field in central Japan was used as a soil sample. Soil microbial respiration activity was depressed with the increase of CO 2 concentration in ventilated air from 0 to 1000 ppmv. At 1000 ppmv, the respiration rate was less than half of that at 0 ppmv. Thus, it is likely that soil respiration rate is overestimated by the alkali absorption method, because CO 2 concentration in the absorption chamber is much lower than the normal level. Metabolic responses to CO 2 concentration were different among groups of soil microorganisms. The bacteria actinomycetes group cultivated on agar medium showed a more sensitive response to the CO 2 concentration than the filamentous fungi group.