Nitrous Oxide Emissions from Ephemeral Wetland Soils are Correlated with Microbial Community Composition

Nitrous oxide (N(2)O) is a greenhouse gas with a global warming potential far exceeding that of CO(2). Soil N(2)O emissions are a product of two microbially mediated processes: nitrification and denitrification. Understanding the effects of landscape on microbial communities, and the subsequent influences of microbial abundance and composition on the processes of nitrification and denitrification are key to predicting future N(2)O emissions. The objective of this study was to examine microbial abundance and community composition in relation to N(2)O associated with nitrification and denitrification processes over the course of a growing season in soils from cultivated and uncultivated wetlands. The denitrifying enzyme assay and [Formula: see text] pool dilution methods were used to compare the rates of denitrification and nitrification and their associated N(2)O emissions. Functional gene composition was measured with restriction fragment length polymorphism profiles and abundance was measured with quantitative polymerase chain reaction. The change in denitrifier nitrous oxide reductase gene (nosZ) abundance and community composition was a good predictor of net soil N(2)O emission. However, neither ammonia oxidizing bacteria ammonia monooxygenase (bacterial amoA) gene abundance nor composition predicted nitrification-associated-N(2)O emissions. Alternative strategies might be necessary if bacterial amoA are to be used as predictive in situ indicators of nitrification rate and nitrification-associated-N(2)O emission.