Contrasting CH 4 flux responses to distinct drought regimes and nitrogen enrichment in a temperate steppe

Summary Drought and nitrogen (N) deposition alter greenhouse gas fluxes, but how distinct drought scenarios interact with N enrichment to regulate the methane (CH 4 ) sink remains poorly understood. We conducted a 4‐yr field experiment in a temperate steppe to examine CH 4 fluxes under three drought regimes – early‐season intense drought (ID), mid‐season chronic drought (CD), and mid‐season reduced rainfall frequency (RF) – and N addition. CH 4 uptake and its driving mechanisms were assessed through field measurements and structural equation modeling, focusing on the interplay between soil physicochemical properties, microbial abundance, and plant‐mediated emissions. All drought treatments reduced the CH 4 sink with divergent temporal dynamics; reduced RF caused the most persistent reduction, while N addition alleviated the inhibitory effects of CD. These shifts were driven by distinct mechanisms: ID acted via lowering previous‐year belowground net primary productivity and increasing dissolved organic N, CD functioned through increased Artemisia frigida cover and reduced arbuscular mycorrhizal fungal abundance, and RF suppressed uptake via the morphological expansion of A. frigida . We conclude that CH 4 sink stability is highly sensitive to drought regime, and that the morphological expansion of specific plants such as A. frigida may partially offset the soil CH 4 sink.