Role of Fungi in N2O Emissions from Nitrogen-Fertilized Lawn Soil

Urban lawns are a predominant form of vegetation in sports grounds and greenbelts. Nitrogen (N) fertilization is widely used to sustain lawn productivity. However, it also promotes nitrous oxide (N2O) emissions, a potent greenhouse gas. The microbial mechanisms underlying N2O emissions from fertilized lawn soils remain poorly understood. In this study, we conducted a controlled incubation experiment with four N application rates [0 (N0), 100 (N100), 200 (N200), and 300 kg·ha−1·yr−1 (N300)] to investigate N2O emissions and associated microbial processes in urban lawn soil. Biological inhibitors combined with high-throughput sequencing were used to quantify the inhibitor-sensitive fraction of fungi and bacteria contributing to N2O emissions. Our results showed that N fertilizer significantly increased N2O emissions, with the highest emission observed under N200. The fungi inhibitor-sensitive fraction accounted for ~45% of total N2O emissions, significantly higher than that of bacteria (~31%). Dominant fungal phyla included Ascomycota, Basidiomycota, and Zygomycota, with N fertilization significantly increasing the relative abundance of Ascomycota and decreasing that of Basidiomycota. Redundancy analysis revealed strong positive correlations between Ascomycota abundance and N2O emissions across N treatments. At the genus level, Pyrenochaetopsis, Myrothecium, and Humicola were positively associated with N2O production and identified as key functional taxa. These findings demonstrate that moderate N fertilization can disproportionately stimulate fungal-driven N2O emissions in urban lawns. The results provide a scientific basis for optimizing N fertilization strategies in green spaces, with implications for N policy and sustainable landscape management.