UC Santa Barbara

Soil processes govern the largest terrestrial carbon pool, but describing the complexmechanisms that control these processes has proven difficult. A soil region particularly important to terrestrial C cycling is the rhizosphere and its underlying mechanisms. Rhizosphere mechanisms are complicated to experimentally capture because their spatial and temporal micro-scale (μm - cm) dynamics fall outside of the methodological reach of traditional experimental techniques. By employing microdialysis to simulate rhizosphere dynamics and simultaneously observing pCO2 with the non-toxic and stable fluorophore 8- hydroxypyrene-1,3,6-trisulfonic acid (HPTS), we are able to simplify and explore otherwise complicated microbial processes in a manner that minimizes disturbances. With the microdialysis system, an area of increased respiration around the microdialysis tip was successfully established and measured in the majority of replicates in a 24 hr time-series via a ratiometric fluorescence analysis. Because this method allows for the simulation of root exudation and analysis of subsequent microbial activity, it is a potential tool to study rhizosphere processes in a laboratory setting, though further development is needed.