Factors influencing the calorespirometric ratios of soil microbial metabolism

Discerning Microbially Mediated Processes During Redox Transitions in Flooded Soils Using Carbon and Energy Balances

“…Peaty Paddy Soil Vietnam Silty clay loam 3.9 9.4 (0. an intercept close to 0, suggesting an average R q /R CO2 of 650 kJ mol −1 CO 2 , which is similar to previously reported values for saturated soils (Barros et al, 2016). Also shown in Figure 2 is the calculated heat output from Equation 1(open diamond symbols, thin solid regression line), assuming (i) all CO 2 was produced from O 2 consumption and (ii) that the average NOSC of initial soluble C ( Table 3) is representative of the substrate used.…”

“…This is technically not an exception from the rule represented in Equation 1, but a matter of knowing which substrate was used for the metabolic reaction, which is difficult in complex systems. Because R q /R CO2 depends on the oxidation state of the substrate, deviations from the predicted value in a fully aerobic system can be interpreted as an indication that a more reduced (higher R q /R CO2 ) or more oxidized (lower R q /R CO2 ) substrate than predicted was used (Barros et al, 2016).…”

“…In well-aerated, moist soils, the calorespirometric ratio, R q /R CO2 (heat dissipation per unit CO 2 produced), varies depending on soil management and land use history (e.g., fertilization, deforestation, reforestation, crop rotations) (Barros Pena et al, 2014;Herrmann and Bölscher, 2015;Barros et al, 2016;Bölscher et al, 2016) and this has been linked to differences in microbial community composition (Bölscher et al, 2016) and organic matter sources (Barros et al, 2016). Such evaluations are based on the thermodynamic relationship between heat and respiration in aerobic systems at steady-state (i.e., no growth), where R q /R CO2 is dependent only on the oxidation state of the substrate (Hansen et al, 2004):…”

Differences in substrate use efficiency: impacts of microbial community composition, land use management, and substrate complexity

“…5). Furthermore, the calorespirometric ratio has the potential for combined investigations 405 of substrate use efficiency, substrate quality and metabolic pathways (Barros et al 2016). It should be noted that 406 calorespirometric ratios varied substantially, but this variation could be reduced, if heat and CO 2 production are 407 measured in the same sample (Barros et al 2011;Herrmann and Bölscher 2015).…”

Editorial: Environmental Bioenergetics

“…However, this has not been rigorously tested experimentally, but in recent years, scientists in a number of fields have increasingly shown interest in quantifying how bioenergetics constrain and define ecosystem functioning. For example, organic matter in soils has distinct energetic signatures, e.g., energy densities and activation energies (Barré et al, 2016;Williams et al, 2018), and microbial bioenergetics provides empirical data for mechanistic models of carbon turnover in soils, work that is relevant to climate change (Sparling, 1983;Herrmann et al, 2014;Barros et al, 2016;Bölscher et al, 2017). Furthermore, geochemists have quantified the amount of chemolithotrophic energy available for microorganisms in a number of extreme environments to infer the dominant metabolic activities (e.g., McCollom and Shock, 1997;Shock et al, 2010;Osburn et al, 2014).…”