Sequential Abiotic-Biotic Processes Drive Organic Carbon Transformation in Peat Bogs

Peatlands, which store one third of the terrestrial carbon (C), are subject to large disturbances under a changing climate. It is crucial to understand how microbial and physiochemical factors affect the vulnerability of these large C stores to predict climate-induced greenhouse gas fluxes. Here, we used a combination of mass spectrometry and spectroscopy techniques, to understand sequential biotic and abiotic degradation pathways of Sphagnum fallax leachate in an anaerobic incubation experiment, in the presence and absence of microorganisms. Removal of microorganisms was carried out by passing aqueous samples through 0.2-mu m filters. Our results revealed that S. fallax leachate degradation by abiotic reactions is a significant contributor to CO2 production. Further, abiotic factors, such as low pH, are responsible for partial dissolved organic carbon (DOC) degradation that produces bioavailable compounds that shift microbial metabolic pathways and stimulate respiration in peat bogs. Acid-catalyzed hydrolysis of Sphagnum- produced glycosides can provide the microbial communities with glucose and stimulate microbial respiration of DOC to CO2. These results, while unique to peatlands, demonstrate the importance and underscore the complexity of sequential abiotic and biotic processes on C cycling in peat bogs. It is therefore crucial to incorporate abiotic degradation and sequential below-ground biotic and abiotic interactions into climate models for a better prediction of the influence of climate change on DOC stability in peatlands. These findings might not be representative of other ecosystems with different environmental conditions including mineral-rich peatlands and plant matter in surface peat horizons that comprise discrete microbial populations, and DOC composition.

Automated summary

The degradation of Sphagnum fallax leachate by abiotic reactions is a significant contributor to CO2 production, while abiotic factors like low pH lead to partial dissolved organic carbon degradation, stimulating microbial metabolic pathways. Acid-catalyzed hydrolysis of Sphagnum-produced glycosides provides glucose to microbial communities, enhancing microbial respiration of DOC to CO2. Incorporating abiotic degradation and sequential below-ground biotic and abiotic interactions into climate models is crucial for predicting the impact of climate change on DOC stability in peatlands.