<p>Nitrogen (N) input enhances N transformations, resulting in harmful environmental impacts by accelerating N loss. However, it remains unclear whether the effects of long-term N inputs on N transformations persist after N addition was ceased. We examined the changes in the communities and activities of ammonia oxidizers in an alpine meadow that underwent 15&#xa0;years of nutrient addition followed by 7&#xa0;years of nutrient cessation. Our results showed that plant N, soil total N, and available N returned to control levels seven years after nutrient addition stopped, whereas nitrification rates, mean N₂O emissions, and ammonia-oxidizing bacteria (AOB) abundance remained elevated. Network complexity among AOB, ammonia-oxidizing archaea (AOA), and comammox <i>Nitrospira</i> was higher in nutrient cessation plots than in control plots. The elevated soil nitrification pattern under nutrient addition was primarily driven by high soil N availability from exogenous N inputs. In contrast, under nutrient cessation, enhanced microbial N cycling sustained the elevated soil nitrification pattern. Therefore, our findings suggest that direct measurements of soil and plant N may not sufficiently capture the recovery of N transformations, and that legacy effects of nutrient addition on N cycling microbes and their activities may persist for many years.</p>