Response and recovery of nosZ abundant and rare subcommunities to organic amendment and nitrification inhibitor disturbances, with implications for N2O emissions

Clarifying the mechanisms underpinning the responses of abundant and rare taxa of the nitrous oxide reductase (nosZ) gene to fertilization disturbances is beneficial for understanding the relationships between N₂O reduction and the nosZ community. Here, we compared the species richness, composition, and abundance of rare and abundant nosZ taxa and their community resistance and resilience within 85 days after different fertilization disturbances, i.e., chemical N anole (CF), chemical N + cattle manure (CM), and cattle manure + nitrification inhibitor nitrapyrin (CP). Our results showed that CM and CP disturbances significantly increased the species richness and α-diversity of the whole nosZ community (P < 0.05), which was mainly attributed to the changes in rare taxa rather than in the abundant taxa. The Bray–Curtis dissimilarity of community composition (average 0.56) of nosZ rare taxa was significantly greater than that of abundant taxa (average 0.26) after disturbances. The rare subcommunity was sensitive to CM and CP disturbances but was resistant to CF disturbance. The α-diversity and abundance of the nosZ community almost recovered at 85 days after disturbance, more so under CM amendment, while its community composition hardly recovered. The nosZ co-occurrence networks indicated that CM and CP disturbances substantially increased the strength of the connections and degrees and strengthened the co-occurrence relationships among modules compared to the CF disturbance. Furthermore, our results confirmed that the resistance or resilience of rare subcommunity compositions contributed more to the mitigation of N₂O caused by CM and CF disturbances, and these were mainly derived by edaphic factors, including SOC, NO₃⁻, pH, and CEC. Our findings suggested that rare taxa played a dominant role in mediating the resistance and resilience of nosZ communities in agro-soil under environmental disturbances and could significantly influence N₂O emissions.