Assessing microbial communities in agricultural soils and their response to winter freeze-thaw at the field-scale

Van Koppen, Linsey
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University of Guelph

This thesis examines soil microbial communities at a long-term research site in Elora, Ontario aiming to link best management practices to soil greenhouse gas production. The goal was to obtain measurements of the microbial community in contrasting management practices. An in-depth analysis was conducted to understand how field-scale variability in freezing affects the microbial communities responsible for N2O emissions from soil. Soil was sampled over freeze-thaw (FT) cycles, and separated into frozen and thawed soils where N-cycling microbial communities were quantified alongside field-N2O emissions. Lasting differences from cover crops and tillage in both the bacterial and fungal communities were present, indicating sensitivity of the microbial community to aboveground change. Functional genes and transcripts representative of nitrification and denitrification were quantified in both thawed and frozen portions of soil throughout multiple freeze-thaws within the sampling period, with soil freezing and time playing the biggest role in shaping these communities.

Microbial community, Cover crops, freeze-thaw, Nitrous oxide, soil, sustainable agriculture