Associations with minerals play an important role in regulating soil organic carbon (SOC) stability, as mineral-bound SOC may have lower bioavailability compared to SOC not associated with minerals. However, only limited existing literature is available concerning direct analysis of aerobic microbial respiration of mineral-bound SOC. Herein, we investigated the aerobic respiration and bioavailability of ferrihydrite (Fh)-, and silica (SiO2)-bound glucose and formic acid vs. free glucose and formic acid by adding 13C-labelled compounds to the natural soils with indigenous microbial population. Results showed that free glucose and formic acid were respired by 67.0% and 70.6%, respectively within 22-day incubation, while the Fh-bound and SiO2-bound compounds were only respired 8.1 to 25.3% and 1.1 to 25.0%, respectively, and demonstrated that SiO2-bound glucose and formic acid had lower bioavailability compared to Fh-bound compounds, and that all mineral-bound compounds had lower bioavailability vs. free compounds. The priming effects of additional organic compounds on the respiration of endogenous SOC were also minimized by the association with minerals. Reduction in bioavailability and priming effects of organic compounds depends on their sorption on minerals. Our results provide a quantitative evaluation on the impact of SOC mineral association on aerobic respiration and priming effects of fresh input SOC.

Aerobic microbial respiration of mineral-bound organic carbon: Bioavailability and priming effects

255th National Meeting (2018)

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