| Summary: | Cropland ecosystems are significant emission sources of N<sub>2</sub>O, but a limited number of studies have focused on the impact of extreme weather events on N<sub>2</sub>O fluxes from cropland. This present study integrated field observations and model simulations to explore the responses of N<sub>2</sub>O fluxes to extreme weather events in typical rice and wheat rotation croplands in the middle and lower reaches of the Yangtze River (MLRYR) in China. The findings revealed that the studied rice-wheat rotation cropland exhibited a net source of N<sub>2</sub>O over the three-year monitoring period, with annual cumulative N<sub>2</sub>O emissions ranging from 190.4 to 261.8 mg N m<sup>−2</sup>. N<sub>2</sub>O emissions during the rice and wheat growing seasons accounted for 29% and 71% of the total yearly emissions, respectively. Extreme heat events led to a 23% to 32% increase in observed N<sub>2</sub>O emissions from cropland. Observed N<sub>2</sub>O emissions from irrigated rice fields during extreme precipitation events were 45% lower than those during extreme drought events. In contrast, extreme precipitation events raised observed N<sub>2</sub>O emissions from rain-fed wheat fields by 36% compared to the multi-year average, while extreme drought events reduced N<sub>2</sub>O emissions from wheat fields by 20%. Regional simulations indicated that annual cumulative N<sub>2</sub>O emissions from croplands in the MLRYR are projected to increase from 207.8 mg N m<sup>−2</sup> under current climate to 303.4 mg N m<sup>−2</sup> in the future. Given the episodic nature and uncertainties associated with N<sub>2</sub>O emissions from cropland, further validation is necessary for utilizing the model to explore the effects of extreme weather events on N<sub>2</sub>O in cropland ecosystems.
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