Nitrogen deposition enhances soil organic carbon sequestration through plant–soil–microbe synergies

Abstract Boreal forest soil organic carbon (SOC) plays a critical role in mitigating climate change due to its large contribution to the global terrestrial carbon sink. However, the effects of nitrogen (N) deposition on SOC accumulation remain poorly understood in boreal forests. Thus, we conducted a long‐term N addition experiment in a boreal forest to investigate whether and how N addition affects SOC, as well as how this effect is regulated by plant–soil–microbe synergies. We found that SOC significantly increased with N addition, driven by the combined responses of plants, soil and microbes. Specifically, N addition enhanced plant nutrient uptake and photosynthetic capacity, leading to increased plant carbon input. N addition also induced soil acidification due to shifts in plant N preferences, which suppressed decomposition and altered microbial communities by enhancing microbial carbon use efficiency toward higher carbon stabilization. Synthesis . Our study provides a holistic mechanistic understanding of how N addition enhances SOC sequestration through plant–soil–microbe interactions.