PNNL

Abstract

Drying and rewetting of soil stimulates soil carbon emission. The Birch Effect, driven by these cycles, leads to CO2 efflux, which can be monitored using real-time mass spectrometry (RT-MS). Although soil fungi retain water during drought, their contribution to CO2 release during drying-rewetting cycles remains unclear. In this study, we present the first demonstration of integrating micromodels with RT-MS to monitor the Birch Effect by simulating drought and rewetting. Micromodels were inoculated with axenic fungal culture and dried to assess moisture retention. After drying, RT-MS quantified CO2 release upon rewetting with H218O mixtures. Our results showed that soil fungi released CO2 upon rehydration and immediately utilized the external water source at the pore scale by generating subsequent 46CO2. This work is the first to integrate RT-MS with microsystems to investigate pore-scale biogeochemistry and the involvement of fungi in the Birch Effect.