Accumulation of NO 2 − during periods of drying stimulates soil N 2 O emissions during subsequent rewetting

Summary Rewetting of soil might contribute considerably to the annual production of nitrous oxide (N 2 O) in ecosystems subjected to long dry periods. Therefore, it is crucial to elucidate the most important factors responsible for large pulses of N 2 O with rewetting. In this study, we carried out a series of rewetting experiments with soil samples collected from upland and riparian forest, grassland and arable land. We analysed the dynamics of ammonium (NH 4 + ), nitrite (NO 2 − ), nitrate (NO 3 − ) and dissolved organic matter (DOM) of air‐dried soil samples after rewetting. We also analysed the effects of sterilization of soil samples by γ‐irradiation on N 2 O production with rewetting. Furthermore, we explored the effects of rewetting and sterilization on the isotopic composition of N 2 O in the different soil samples. The grassland soil produced the largest amount of N 2 O (64.1 μg N kg −1 ) in 1 hour on rewetting, followed by upland forest soil, whereas it was least for soils from riparian forest and arable land. Gamma irradiation, however, decreased soil N 2 O production from forest soil samples by 30–90% after rewetting, but increased N 2 O production in grassland and arable land soils three‐fold and two‐fold, respectively. Correlation analysis revealed that NO 2 − concentration in the soil samples at the time of rewetting was the most relevant factor that explained soil N 2 O production after rewetting. Furthermore, the addition of NO 2 − before rewetting increased N 2 O production during rewetting more than with additions of NO 3 − and NH 4 + in all soil samples. The 15 N site preference values of N 2 O produced after rewetting were close to 0‰, indicating a denitrification‐related production process according to the classical view. However, additional abiotic processes responsible for soil N 2 O production during rewetting cannot be excluded.HighlightsMechanisms responsible for large N 2 O production during rewetting of soil are not well understood. Nitrite content in dry soil was strongly correlated with N 2 O production after rewetting. The 15 N site preference of the N 2 O produced was close to 0‰ after rewetting. Additional abiotic processes could have contributed to N 2 O formation from NO 2 − .