Thermodynamic Insights into Microbial Energy Turnover in Heterogeneous Soil Systems

Microbial processes drive the turnover of soil organic matter by regulating both matter and energy flows. Although carbon cycling has been extensively studied, microbial energy flows and their modulation under heterogeneous soil conditions remain insufficiently explored. Our work develops a thermodynamically consistent framework for quantifying microbial energy turnover in soils. The framework combines calorespirometric heat flow measurements with carbon flow (CO₂ evolution, substrate consumption and biomass formation), using an enthalpy-based balance approach and newly developed calorespirometric instruments.

Although our primary focus is on thermodynamic constraints and calorimetric quantification, these methods offer a promising route to investigate the consequences of soil heterogeneity. For instance, variations in soil aggregations, water content, redox conditions or the C/N ratio can create spatially distinct microhabitats, that alter local energy turnover and metabolic efficiency. By linking heat and carbon flows to these heterogeneous microenvironments, our approach provides a pathway to assess the energetic impacts of soil heterogeneity across scales.

In this presentation, we introduce a conceptual framework and preliminary data on the use of calorespirometry to link heat production rates with carbon flows, providing a window into microbial energy dynamics in heterogeneous soils. Our work highlights the potential of thermodynamic measurements to complement the structural and biogeochemical characterizations of soil heterogeneity, providing new insights into the energetic constraints that shape microbial activity.