Individual fungal taxa drive community structure change and necromass accumulation increment

Background Conversion of accessible organic compounds to fungal biomass and subsequent necromass is a crucial process for soil organic matter accrual. The contribution of fungal community structure and biomass to necromass accumulation in croplands remain unclear. Results We assessed the fungal necromass increment by amino sugar content in soil of a long-term field experiment after straw return and nitrogen (N) fertilization. The fungal absolute copy number and community structure were assessed by absolute quantitative sequencing technology. Straw input and N-fertilization-induced wheat growth was the main factor in increasing fungal absolute copy number, altering community structure, and consequently boosting necromass accumulation. N fertilization additionally shifted the fungal community structure by alleviating N limitation and balancing the C:N ratio of added material. The fungal community structure, rather than the total absolute copy number, was the best predictor of necromass increment. Specifically, necromass increment were primarily attributed to the rapid growth of individual fungal taxa rather than the keystones in dominant modules. Specifically, the community structure changed towards the aggregation of pathogenic fungi represented by Pyrenochaetopsis and Dokmaia under high straw return and low or no N fertilization scenarios, while in the scenario of co-existence of straw and N fertilization increased the abundance of saprophytic fungi, represented by Ascobolus and Botryotrichum , replaced pathogenic fungi and dominated the community structure change and raised the fungal necromass accumulation. Conclusions In conclusion, individual fungal taxa drive community structure changes and necromass increment.