Nitrogen addition decreases soil aggregation but enhances soil organic carbon stability in a temperate forest

•Detection of soil aggregate stability related to soil organic carbon stability under N addition.•Fine roots play a major role in decreasing soil aggregate stability in response to N addition.•N addition enhances SOC stability with evidence of the decrease in C mineralization.•Stable mixed model revealed the promotion of mineral-associated C formation under N addition.•SOC stability in large macroaggregates was more vulnerable than that in small macroaggregates.