Characterizing temporal and spatial changes to the soil microbiome through the winter transition and freeze-thaw cycles in agricultural fertilizer amended soils

Largely overlooked, microbial activity in soil persists under snow and ice throughout the winter transition and reaches its apex during thaw events. With the onset of climate change the active layer of soils will experience colder temperatures as it loses its snowpack insulation and consequently will undergo a higher frequency of freeze-thaw cycles. These changes will have downstream effects on the underlying geochemistry of soils and subsequently microbial composition and activity. The result leave unclear implications for the study of climate change, agricultural management, and biogeochemical cycling. Thus the objective of this research is to characterize the changes in microbial diversity and bioenergetics as a function of the changing environmental metrics of soil geochemistry and nutrient availability throughout the winter transition. Further the efficacy of pre-winter fertilizer amendments will be explored from concerns of decreasing potency as thaw events may allow for early onset microbial growth and consumption of the fertilizer. The data contained here is pursuant to the “Winter Soils Processes in Transition” project under the broader Global Water Futures program funded by Canada First Research Excellence Fund.

Agricultural soil from the rare Charitable Research Reserve, located in Cambridge, Ontario, was homogenized and used to pack four soil columns. Laboratory controlled conditions allowed for dynamically simulating a climate model of the winter transition months to a period of 55 days, including adjustments to temperature and precipitation. Insulation of the columns allowed for realistic simulation of the natural soil temperature gradient across depth and time. Two of the columns were amended with fertilizer while two were left as controls. This setup allowed for high resolution temporal and spatial soil sampling for high-throughput sequencing of microbial diversity (16S and ITS rRNA amplicon sequencing) for characterization of the changes to unique bacterial, archaeal, and fungal populations. Further adenosine triphosphate concentrations from the soil samples allowed for tracking of microbial activity over the course of the experiment. Changes to the microbiome are analyzed as a function of the changing geochemical properties and nutrient composition of the soil measured in collaboration with the Ecohydrology Research Group Laboratory at the University of Waterloo.

Hug, L., Jensen, G., Krogstad, K., and Rezanezhad, F. (2019). Characterizing temporal and spatial changes to the soil microbiome through the winter transition and freeze-thaw cycles in agricultural fertilizer amended soils. Waterloo, Canada: Canadian Cryospheric Information Network (CCIN). Unpublished Data.

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