Evaluation of the Relationship of Climate on Primary versus Secondary Fermentation of Poor Fen Northern Peatlands Using DNA-Stable Isotope Probing

Abstract:

The influence of primary versus secondary fermentation on methanogenesis of poor fen Northern peatland soil incubations was investigated. To assess the relationship of climate on primary and secondary fermentation and its effect on methane production, we study four poor fens with similar hydrology and geochemistry along a climate gradient in four biomes: tundra (Daring Lake, NWT), boreal forest (Lutose, AB) and temperate broadleaf and mixed forest (Bog Lake, MN and Chicago Bog, NY). Anaerobically sampled soils from each site were homogenized, pre-incubated and amended with: 13C-Glucose as a proxy for primary fermentation or 13C-Propionate as a proxy for secondary fermentation.

The rate of glucose consumption ranged from 19.57-42.60 ppm day^-1, with Chicago Bog having the highest rate of consumption and Bog Lake having the lowest rate of consumption. The CH₄:CO₂ of glucose incubations ranged from 0.01-0.9, and generally increased with decreasing mean annual temperature, suggesting that as mean annual temperature increases methanogenesis could compete with other anaerobic reactions as the terminal decomposition reaction. The rate of propionate consumption ranged from 2.79-5.25 ppm day^-1, with Chicago Bog having the lowest rate of consumption (opposite range than glucose) and Lutose having the highest rate of consumption. The CO₂: CH₄ of propionate incubations ranged from 1.6-31.6.

DNA-SIP labelling profiles were completed, resolved and sequenced via 16S MiSeq amplicon sequencing. Differential distribution and buoyant density is being analyzed to identify active microbes performing primary versus secondary fermentation. These analyses facilitate a more in depth understanding of the intermediary ecosystem metabolism of poor fen type northern peatlands and methane production under different climate regimes.