Frontiers in Microbiology (Jun 2011)
Nitrous oxide emissions from ephemeral wetland soils are correlated with microbial community composition
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 (DEA) and 15NO3- 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 (RFLP) profiles and abundance was measured with quantitative polymerase chain reaction (QPCR). The change in denitrifier nitrous oxide reductase gene (nosZ) abundance and community composition was a good predictor of net soil N2O emission. However, neither AOB ammonia monooxygenase (bacterial amoA) nor AOA ammonia monooxygenase (archaeal amoA) gene abundance and composition predicted nitrification-associated N2O emissions. Alternative strategies might be necessary if bacterial or archaeal amoA are to be used as predictive in situ indicators of nitrification rate and nitrification-associated N2O emission.
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