Warmer and drier conditions alter the nitrifier and denitrifier communities and reduce N2O emissions in fertilized vegetable soils.

Nitrous oxide (N 2 O) is a potent greenhouse gas and is mainly produced from agricultural soils especially vegetable soils with large N fertilizer input. How future projected climate change may impact on the N 2 O emissions and the related key (de)nitrifier communities in such ecosystem is poorly understood. The aim of this field study was to determine the interactive effects of a simulated warmer and drier climate on (de)nitrifier communities and N 2 O emissions in a vegetable soil. A warmer (+3.3 °C) and drier climate (−14.4% soil moisture content) was created with greenhouses with or without urea N fertilizer application. The variation of microbial population abundance and community structure of Ammonia-oxidizing archaea (AOA), bacteria (AOB) and denitrifiers ( nirK/S , nosZ ) were determined using Real time-PCR and sequencing. The results showed a strong interactive effect of simulated climate change with N fertilizer applications, whereby the impacts of warmer and drier conditions on the microbial communities and N 2 O emissions were more evident when N fertilizer was applied. The simulated warmer and drier conditions in the greenhouses significantly decreased N 2 O emissions largely due to the drier soil conditions. The abundance and community structure of AOB showed more rapid responses than AOA under the simulated climate conditions when N fertilizer was applied. Changes of AOB community structure were significantly correlated with soil moisture content and NH 4 + -N concentration. The simulated climate change did not affect the nirS gene abundance, but significantly increased nirK gene abundance, and significantly decreased nosZ gene abundance with urea application. N 2 O emissions were positively correlated with the bacterial amoA abundance and with the ratio of nirK / nosZ gene abundance. Therefore, bacterial amoA , nirK- and nosZ- type denitrifiers are the dominant microbial communities which were affected by the simulated climate conditions and are thus critically important for N cycling in vegetable soils under a changing climate. [ABSTRACT FROM AUTHOR]