Use of microcalorimetry to study microbial activity during the transition from oxic to anoxic conditions |
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Authors: | Torsten Vor Jens Dyckmans Heiner Flessa Friedrich Beese |
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Institution: | 1.Institute of Soil Science and Forest Nutrition, University of G?ttingen, Büsgenweg 2, 37077 G?ttingen, Germany, |
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Abstract: | Microbial heat production is a nonspecific measure for microbial activity irrespective of O2 availability in soils. In a series of long-term batch microcalorimeter experiments with closed ampoules, we examined the microbial activity in glucose-amended soil aggregates from different soil depths of a clay forest soil during the transition from aerobic to anaerobic conditions. Furthermore, the influence of the soil aggregate size on the long-term metabolic heat production was examined. Heat output curves showed a distinct pattern for soil samples from different soil depths and aggregate sizes and led to the following conclusions: 1. Microbial biomass and microbial activity strongly decreased with increasing soil depth as well as increasing soil aggregate size despite relatively constant organic C concentrations. 2. The transition from aerobic to anaerobic conditions led to a considerable drop in microbial activity. However, based on the energy balance, 10-26% of the heat production during the aerobic phase is attributable to anoxic or partly anoxic metabolism. 3. After O2 exhaustion, a lag phase of low but constant heat output was observed, followed by a peak of anaerobic metabolic activity. Heat production during the lag phase was hypothesised to be an indicator for the biomass of facultatively anaerobic microorganisms in the soil. |
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