Researchers at Sorbonne Universite found that electrical conductivity can act as a proxy for how fast microbes in drying soil release carbon. In controlled lab experiments, they dried soil samples from tilled and conservation agriculture plots, then measured both CO2 flux and the movement of ions through the water-filled pore network. The two tracked together: as water films became more disconnected, respiration and conductivity both dropped. The relationship held within the diffusion-limited moisture range and was stronger in disturbed soils. That matters because soil holds more organic carbon than the atmosphere and vegetation combined. Most carbon models currently rely on empirical curves to describe moisture effects on respiration. If field sensors can measure conductivity the same way, we could monitor soil carbon release without digging up samples, and improve estimates of how drought and land management change the largest terrestrial carbon reservoir.
