Temporal-scale-dependent mechanisms of forest soil nitrous oxide emissions under nitrogen addition

Nitrous oxide (N2O) emissions from forest soils are typically intensified under elevated anthropogenic nitrogen (N) deposition, likely due to increased N availability. However, the extent to which these emissions are linked to N availability across different timescales remains poorly understood. Here we investigated the temporal-scale-dependent mechanisms of N2O emissions in a subalpine forest under N-addition, using hourly-resolved N2O measurements. Our findings revealed that N-addition induced both pulse emissions and a long-lasting effect on soil N2O emissions. The pulse emissions occurred immediately after each N-addition, indicating a strong linkage between the pulse events and elevated Navailability. However, variations in annual N2O emissions were not directly regulated by Navailability but were instead explained by denitrifying microbial functional genes ratio. A global meta-analysis further confirmed the importance of microbial functional genes in regulating N2O emissions in natural terrestrial ecosystems. Our results suggest a crucial role of microbial functional genes in predicting annual N2O emissions from forest soils.