Applicability of Radiotracer Methods of Measuring (14)CO(2) Assimilation for Determining Microbial Activity in Soil Including a New In Situ Method

The applicability of two methods (pyrolysis gas chromatography and acidification-wet oxidation) for determining (14)CO(2) incorporation into soil microorganisms was investigated. Both methods were able to distinguish biologically incorporated (14)C from abiotically adsorbed (14)C, but to varying degrees, there being a larger carryover of abiotic (14)C into the organic fraction and a higher percentage of assimilated (14)C in the organic fraction with the wet oxidation method. Using (14)C assimilation as a measure, it was possible to determine microbial activities in soils of diverse properties under a variety of conditions, including polar soils under harsh environmental conditions. Both light and dark (14)CO(2) fixation was measurable. (14)CO(2) assimilation was not always proportional to the enumerable microorganisms. A new design for measurement of microbial activity in situ enabled measurement of total C influx (primary productivity) into soils with minimal perturbation to the natural soil e. cosystem.