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Soil moisture (SM) is essential to microbial nitrogen (N)‐cycling networks in terrestrial ecosystems. Studies have found that SM–atmosphere feedbacks dominate the changes in land carbon fluxes. However, the influence of SM–atmosphere feedbacks on the N fluxes changes, and the underlying mechanisms remain highly unsure, leading to uncertainties in climate projections. To fill this gap, we used in situ observation coupled with gridded and remote sensing data to analyze N2O fluxes emissions globally. Here, we investigated the synergistic effects of temperature, hydroclimate on global N2O fluxes, as the result of SM–atmosphere feedback impact on N fluxes. We found that SM–temperature feedback dominates land N2O emissions by controlling the balance between nitrifier and denitrifier genes. The mechanism is that atmospheric water demand increases with temperature and thereby reduces SM, which increases the dominant N2O production nitrifier (containing amoA AOB gene) and decreases the N2O consumption denitrifier (containing the nosZ gene), consequently will potential increasing N2O emissions. However, we find that the spatial variations of soil–water availability as a result of the nonlinear response of SM to vapor pressure deficit caused by temperature are some of the greatest challenges in predicting future N2O emissions. Our data‐driven assessment deepens the understanding of the impact of SM–atmosphere interactions on the soil N cycle, which remains uncertain in earth system models. We suggest that the model needs to account for feedback between SM and atmospheric temperature when estimating the response of the N2O emissions to climatic change globally, as well as when conducting field‐scale investigations of the response of the ecosystem to warming. [ABSTRACT FROM AUTHOR]

Earth's ecosystems are increasingly threatened by "hot drought," which occurs when hot air temperatures coincide with precipitation deficits, intensifying the hydrological, physiological, and ecological effects of drought by enhancing evaporative losses of soil moisture (SM) and increasing plant stress due to higher vapor pressure deficit (VPD). Drought‐induced reductions in gross primary production (GPP) exert a major influence on the terrestrial carbon sink, but the extent to which hotter and atmospherically drier conditions will amplify the effects of precipitation deficits on Earth's carbon cycle remains largely unknown. During summer and autumn 2020, the U.S. Southwest experienced one of the most intense hot droughts on record, with record‐low precipitation and record‐high air temperature and VPD across the region. Here, we use this natural experiment to evaluate the effects of hot drought on GPP and further decompose those negative GPP anomalies into their constituent meteorological and hydrological drivers. We found a 122 Tg C (>25%) reduction in GPP below the 2015–2019 mean, by far the lowest regional GPP over the Soil Moisture Active Passive satellite record. Roughly half of the estimated GPP loss was attributable to low SM (likely a combination of record‐low precipitation and warming‐enhanced evaporative depletion), but record‐breaking VPD amplified the reduction of GPP, contributing roughly 40% of the GPP anomaly. Both air temperature and VPD are very likely to continue increasing over the next century, likely leading to more frequent and intense hot droughts and substantially enhancing drought‐induced GPP reductions. [ABSTRACT FROM AUTHOR]