Autor:innen:
Eliana Di Lodovico | Universität Koblenz · Landau - Campus Landau, Fortstraße 7, 76829 Landau in der Pfalz; Helmholtz Zentrum für Umweltforschung - UFZ, Permoserstraße 15, 04318 Leipzig
Dr. Christian Fricke | Universität Koblenz · Landau - Campus Landau, Fortstraße 7, 76829 Landau in der
Dr. Maximilian Meyer | Universität Koblenz · Landau - Campus Landau, Fortstraße 7, 76829 Landau in der Pfalz | Germany
Prof. Dr. Gabriele Schaumann | Universität Koblenz · Landau - Campus Landau, Fortstraße 7, 76829 Landau in der Pfalz | Germany
Dr. Thomas Maskow | Germany
Soil microbial communities are the main catalyst of the carbon (C) cycle in the soil, playing a key role in the degradation of organic compounds. The fluxes of C driven by the microorganisms are always coupled with the release of heat via the law of Hess. Several models show that the simultaneous measurement of respiration (CO2 evolution rate) and heat production rate, called calorespirometry (CR), can provide information about the fate of degraded organic substances or SOM [1][2]. CR was already established in soil sciences, but the current approach still has several limitations (low CO2 partial pressure, small sample size mimicking large soil systems, oxygen limitations, indirect CO2 measurements, and low sample throughput).
In order to overcome these limitations, we combined a conventional soil respirometer with perfectly matched calorimetric measuring units and compared our new calorespirometric approach with the current approach in CR. In the latter, both (metabolic heat and respiration) are measured calorimetrically, and for the CO2 evolution, the calorimetric ampoules are equipped with NaOH-solution (CO2 trap), and the adsorption heat is measured. In the new approach, the metabolic heat is measured calorimetrically, while the CO2 released is measured conductometrically using a KOH-solution (CO2 trap). The two approaches have complementary advantages, the current shows a higher sensitivity for the calorimetric measurements and has a stable baseline and a clear offset, the new one allows continuous CO2 measurements, larger sample sizes, higher sample throughput, and prevents oxygen limitation. Despite the differences, both approaches have in common the calorespirometric ratio, an important parameter to evaluate the microbial metabolic pathways and the SOM dynamics.
[1] Wadsö L. and Hansen L.D., Calorespirometry of terrestrial organisms and ecosystems, Methods 76 (2015) 11–19
[2] Chakrawal A. et al., Quantifying microbial metabolism in soils using calorespirometry – A bioenergetics perspective, Soil Biology and Biochemistry 148 (2020) 107945