Abstract
Nitrous oxide (N2O) is a greenhouse gas with a global warming potential far exceeding that of CO2. Soil N2O 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 N2O emissions. The objective of this study was to examine microbial abundance and community composition in relation to N2O 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 pool dilution methods were used to compare the rates of denitrification and nitrification and their associated N2O 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 N2O emission. However, neither ammonia oxidizing bacteria ammonia monooxygenase (bacterial amoA) gene abundance nor composition predicted nitrification-associated-N2O emissions. Alternative strategies might be necessary if bacterial amoA are to be used as predictive in situ indicators of nitrification rate and nitrification-associated-N2O emission.
Highlights
Nitrous oxide (N2O) is a greenhouse gas with 300 times the global warming potential of CO2 (Jungkunst and Fiedler, 2007) and can be produced by nitrification (Avrahami et al, 2002; Mintie et al, 2003) and denitrification (Cavigelli and Robertson, 2000; Rich et al, 2003)
Contrary to bacterial amoA abundance, denitrifier nosZ abundance declined during the sampling season in all soils (Figures 2A,E)
While temporal abundance of denitrifier nosZ appears to be related to potential soil N2O emissions, temporal abundance of bacterial amoA abundance was negatively correlated with nitrification and nitrification-associated-N2O
Summary
Nitrous oxide (N2O) is a greenhouse gas with 300 times the global warming potential of CO2 (Jungkunst and Fiedler, 2007) and can be produced by nitrification (Avrahami et al, 2002; Mintie et al, 2003) and denitrification (Cavigelli and Robertson, 2000; Rich et al, 2003). Available C, N, and O2 are three proximal factors that control the rates of N2O production/consumption via nitrification and denitrification (Svensson et al, 1991; Cavigelli and Robertson, 2000; Avrahami et al, 2002). The effects of land-use mainly influence nutrient availability (through fertilization and cropping) and soil disturbance (through tillage; Bruns et al, 1999; Stres et al, 2004)
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