Shifts of arbuscular mycorrhizal fungal functioning along a simulated nitrogen deposition gradient

The deposition of atmospheric nitrogen can significantly boost the amount of nitrogen available in various ecosystems, potentially altering the mutualistic association between arbuscular mycorrhizal fungi (AMF) and their host plants. Nevertheless, the precise mechanisms and the degree to which externally induced nitrogen-related changes in AMF functionality might impact Sorghum bicolor (L.) Moench, a plant known for its high mycorrhizal colonization, remains unclear. In this study, the mycorrhizal response affected by environmental N enrichment was addressed by conducting a glasshouse experiment, and four fertilization treatments (N1, N2, N3, and N4, 0, 15, 30, and 60 kg N hm⁻¹ a⁻¹, respectively) were used to simulate N deposition differences over the mycorrhizal response. The changes in mycorrhizal colonization and plant variables during different AMF and N fertilizer applications were investigated. When the gradient's nitrogen levels increased, the mycorrhizal growth response and mycorrhizal nitrogen response showed a pattern of first dropping and then increasing. N-induced changes in the mycorrhizal response were associated with vesicular colonization, arbuscular colonization, and root-length colonization. The variation in the mycorrhizal response over the N concentration gradient highlights the critical role of AMF in agroecosystems.