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.

Extreme precipitation events (EPEs) are projected to become more frequent and intense due to global warming. Understanding how coastal groundwater levels respond to and recover from these severe events is important for estuarine ecosystems to adapt to global change. Numerical model and non-EPE scenario simulation were used to examine groundwater level recovery time (RT) after Super Typhoon Lekima, which triggered EPEs that resulted in groundwater rise and widespread flooding in the Yellow River Delta (YRD). The three-day rainfall during Lekima totaled 290.9 mm, equivalent to 50 % of the annual rainfall for 2019 (581.5 mm), leading to a general rise in groundwater levels. Groundwater recovery to EPE can be divided into two types: inland and coastal. The RT of groundwater levels in monitoring wells in inland areas ranged from 12 to 89 days, with an average of 56.2 days, and there was spatial variation. However, groundwater levels in monitoring wells close to the coast may not recover. Differences in recovery are reflected in the land-sea gradient, with RT gradually increasing from inland highlands to coastal depressions and lowlands. The results showed that inland aquifers were more resistant to EPEs, while coastal aquifers were less resistant. In addition, EPE can cause groundwater flooding, and areas at lower altitude and close to the sea are more sensitive to flooding. Estuarine groundwater and the ecological processes on which it depends are profoundly affected by the direct and legacy effects of EPEs, including salt contamination, widespread flooding, crop damage, and reduced biodiversity. The study of this event provides case support for the response of estuarine groundwater to EPEs, while highlighting the importance of continuous monitoring.