Ammonia-oxidizing bacteria are sensitive and not resilient to organic amendment and nitrapyrin disturbances, but ammonia-oxidizing archaea are resistant

Understanding the response of soil microorganisms to environmental disturbance is critical to predicting rates of ecosystem processes. Ammonia-oxidizing bacteria (AOB) and archaea (AOA) drive the rate-limiting step of nitrification. However, the effect of fertilization disturbances (organic amendments and biochemical inhibitors) on the resistance and resilience of communities of AOB and AOA is unknown. Here, we explored the responses of the AOA and AOB communities (based on abundance, diversity, richness and composition) after disturbances caused by the application of inorganic N (urea alone, IN), an organic amendment (cattle manure, OA), a urease inhibitor (NBPT) and a nitrification inhibitor (nitrapyrin) or their combination in a calcareous soil after 85 days. A relative quantitative index of both the resistance (RS) and resilience (RL) was used to assess the variation of gene communities. The AOB community α-diversity, richness and abundance rapidly increased at 7 days after IN and OA (P < 0.05) compared to CK (without any disturbances), whereas those factors decreased after OA + nitrapyrin or OA + nitrapyrin + NBPT application. The RS indices of AOA abundance and diversity were higher than those of AOB after the IN, OA and nitrapyrin disturbances, indicating AOA were more resistant. NMDS analysis showed that the changes in the composition of the AOB community were observed both at 7 and 85 days after OA + nitrapyrin disturbance. In contrast, the AOA community composition did not change within 85 days after these disturbances. Moreover, the RL indices of AOB community were much lower than those of AOA. Soil pH and ammonium (NH4+) played major roles in the changes in the AOB community in response to disturbance. Taken together, our results highlight that AOB are sensitive and not resilient to organic amendment or nitrapyrin disturbance, while AOA are resistant to these disturbances in calcareous soil.