Nitrous oxide (N2O) is the third most important greenhouse gas, and can damage the atmospheric ozone layer, with associated threats to terrestrial ecosystems. However, to date it is unclear how extreme precipitation and nitrogen (N) input will affect N2O emissions in temperate desert steppe ecosystems. Therefore, we conducted an in -situ in a temperate desert steppe in the northwest of Inner Mongolia, China between 2018 and 2021, in which N inputs were combined with natural extreme precipitation events, with the aim of better understanding the mechanism of any interactive effects on N2O emission. The study result showed that N2O emission in this desert steppe was relatively small and did not show significant seasonal change. The annual N2O emission increased in a non-linear trend with increasing N input, with a much greater effect of N input in a wet year (2019) than in a dry year (2021). This was mainly due to the fact that the boost effect of high N input (on June 17th 2019) on N2O emission was greatly amplified by nearly 17-46 times by an extreme precipitation event on June 24th 2019. In contrast, this greatly promoting effect of high N input on N2O emission was not observed on September 26th 2019 by a similar extreme precipitation event. Further analysis showed that soil NH4+-N content and the abundance of ammonia oxidizing bacteria (amoA (AOB)) were the most critical factors affecting N2O emission. Soil moisture played an important indirect role in regulating N2O emission, mainly by influencing the abundance of amoA (AOB) and de-nitrification functional microorganisms (nosZ gene). In conclusion, the effect of extreme precipitation events on N2O emission was greatly increased by high N input. Furthermore, in this desert steppe, annual N2O flux is co-managed through soil nitrification substrate concentration (NH4+-N), the abundance of soil N transformation functional microorganisms and soil moisture. Overall, it was worth noting that an increase in extreme precipitation coupled with increasing N input may significantly increase future N2O emissions from desert steppes.

Significant changes in climate and perturbation from human activities have been reported over the Qinghai -Tibetan Plateau (QTP), likely altering the ecosystem nitrogen (N) cycling and thus N2O emission. So far, a number of studies have reported variabilities of N2O fluxes from background soil conditions, or conducted warming and N addition experiments to test these effects; however, a synthesized understanding of warming and N input on soil N2O emission is still lacking for the QTP. Here, based on available studies published for this region, we investigated spatiotemporal patterns of background N2O fluxes and performed a meta-analysis to examine the warming and N-addition effects on N2O emission. Annual N2O fluxes ranged from-0.33 to 2.14 kg N2O-N ha(-1) yr(-1) (mean =0.73), of which their spatial distributions across ecosystems were mainly reflected by mean annual precipitation. N2O fluxes during growing seasons were generally larger than those in non-growing seasons, but hot moments of N2O emission existed during freeze-thawing periods. Our meta-analysis showed that warming had a significantly negative but minor effect on N2O emission from non-permafrost soils, although the effect varied with warming magnitudes and methods. The negative response of N2O flux to warming could be explained by the associated decrease of soil moisture and enhancement of plant N uptake. In contrast, warming-induced thawing increases soil moisture in permafrost soils, which could stimulate N2O emission. N addition exhibited an overall positive impact on N2O emission over the QTP region, with a moderate emission factor (0.8%) lower than the IPCC value. Considering the moderate N2O emission from background soils (< 1 kg N2O-N ha(-1) yr(-1)) and common N limitation across ecosystems, our findings suggest that climate change and enhanced N inputs may not turn the QTP into a globally significant N2O source in the near future.