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 N availability. However, variations in annual N₂O emissions were not directly regulated by N availability 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. Addition of nitrogen to subalpine forest soil leads to scale-dependent pulses of nitrous oxide emissions and increases in seasonal and annual emissions that were modified by the abundance of microbial functional genes, according to manipulated field experiments.