Nitrogen deposition changes the root nutrient uptake strategies by affecting microbial diversity of the rhizosphere

Abstract

Despite the acknowledged importance of rhizosphere fungi in ecosystem functioning, their role in mediating the effects of environmental changes on plant root nutrient uptake strategies remains inadequately understood. To address this gap, long-term nitrogen addition field experiments were conducted to investigate how rhizosphere fungal diversity influences specific root length, a pivotal indicator of plant nutrient uptake rate. The results of the study showed that nitrogen addition significantly augmented specific root length and rhizosphere fungal diversity in both arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) tree species. However, the effects on rhizosphere fungal diversity differed markedly between the two mycorrhizal types. In AM tree species, nitrogen addition decreased rhizosphere beneficial fungal diversity while increasing the diversity of pathogenic fungi. Conversely, ECM tree species exhibited an increase in rhizosphere beneficial fungal diversity and a reduction in pathogenic fungal diversity under nitrogen addition. Furthermore, we identified a positive correlation between the diversity of rhizosphere pathogens and specific root length under nitrogen addition, while a negative correlation was observed under the control. Structural equation modeling further revealed that the indirect effects of nitrogen addition on SRL were mediated through changes in the diversity of rhizosphere beneficial fungi. These findings suggest that nitrogen addition not only directly influences SRL but also exerts significant indirect effects by altering the microbial composition of the rhizosphere. In summary, the study underscores the substantial impact of long-term nitrogen addition on the interactive mechanism of plant physiological characteristics, mediated by pathogenic and beneficial fungi in the rhizosphere of temperate forests.