Soil properties and fungal community jointly explain NO emissions following N and P enrichment in an alpine meadow.

Nutrient enrichment, such as nitrogen (N) and phosphorus (P), typically affects nitrous oxide (NO) emissions in terrestrial ecosystems, predominantly via microbial nitrification and denitrification processes in the soil. However, the specific impact of soil property and microbial community alterations under N and P enrichment on grassland NO emissions remains unclear. To address this, a field experiment was conducted in an alpine meadow of the northeastern Qinghai-Tibetan Plateau. This study aimed to unravel the mechanisms underlying N and P enrichment effects on NO emissions by monitoring NO fluxes, along with analyzing associated microbial communities and soil physicochemical properties. We observed that N enrichment individually or in combination with P enrichment, escalated NO emissions. P enrichment dampened the stimulatory effect of N enrichment on NO emissions, indicative of an antagonistic effect. Structural equation modeling (SEM) revealed that N enrichment enhanced NO emissions through alterations in fungal community composition and key soil physicochemical properties such as pH, ammonium nitrogen (NH-N), available phosphorus (AP), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN)). Notably, our findings demonstrated that NO emissions were significantly more influenced by fungal activities, particularly genera like Fusarium, rather than bacterial processes in response to N enrichment. Overall, the study highlights that N enrichment intensifies the role of fungal attributes and soil properties in driving NO emissions. In contrast, P enrichment exhibited a non-significant effect on NO emissions, which highlights the critical role of the fungal community in NO emissions responses to nutrient enrichments in alpine grassland ecosystems.