Soil properties and plant community-level traits mediate arbuscular mycorrhizal fungal response to nitrogen enrichment and altered precipitation

Despite the linkage of arbuscular mycorrhizal (AM) fungi to soil-plant interface, how changes in plant community-level traits and soil properties affect AM fungal communities under global changes remains largely unknown. Here, to investigate whether nitrogen (N) enrichment and altered precipitation can influence AM fungal communities through effects on plant community-level traits and soil properties, a six year-long factorial N and precipitation field experiment (N-addition rate: 10 g m−2 year−1; reduced precipitation by 50% and enhanced precipitation by 50%) was conducted in an alpine steppe of the Tibet Plateau. We observed that reduced precipitation decreased AM fungal diversities, while N enrichment decreased AM fungal biomass. Secondly, N enrichment and reduced precipitation shifted plant community composition from bunchgrass dominance (primarily Stipa purpurea) to rhizomatous grass dominance (primarily Leymus secalinus). N enrichment and reduced precipitation also led to a marked shift in AM fungal community composition. More specifically, reduced precipitation enhanced the relative abundance of the dominant taxa Glomus, while the relative abundance of Scutellospora and Diversispora was decreased. In contrast, N enrichment decreased the relative abundance of Scutellospora and Diversispora, while the relative abundance of Glomus was decreased. Structural equation models (SEMs) demonstrated that precipitation regime affected dominant AM fungal taxa via soil pH, while N enrichment affected dominant AM fungal taxa by changes in plant community-level traits. In addition, N- and precipitation-induced shifts in AM fungal community structure were significantly related to canopy photosynthetic rates and soil pH, indicating that canopy photosynthesis and soil pH may mediate the responses in AM fungal communities to enhanced N deposition and precipitation regime. Therefore, our findings may provide previously unidentified insights into N- and precipitation- evoked differential responses of AM fungal communities by linking plant community-level traits and soil properties.