Purpose: Nitrogen deposition due to human activities is known to have a substantial impact on arbuscular mycorrhizal fungi (AMF) community in plant roots. However, the influence of elevated nitrogen on the phylogenetic structure of AMF across fine spatial scales, as well as the mechanisms behind such alterations, are remained poorly understood.

Results: Nitrogen addition significantly increased the phylogenetic alpha diversity (diversity within a plot) and the ‘within-treatment’ phylogenetic beta diversity (dissimilarity among replicate plots) of AMF communities, which resulted in an increased ‘within-treatment’ phylogenetic gamma diversity (overall diversity among all the replicate plots within a treatment). These changes were caused by the relative abundance decline of a dominant genus (Glomus) and an increase in non-dominant genera. Mechanically, nitrogen addition affected phylogenetic alpha diversity mainly by influencing soil properties. Likewise, the increased ‘within-treatment’ dissimilarity of plant community composition and changes in soil properties caused by nitrogen addition and plot distance contributed to an increase in within-treatment phylogenetic beta diversity.

Conclusions: We conclude that deterministic environmental filtering (both abiotic and biotic) and dispersal limitation effect played critical roles in AMF community assembly under global change scenarios. Insightfully, this study provides a mechanistic understanding of the response of AMF to nitrogen addition across fine scales.

We collected 256 root samples of 16 common plant species that occurred along a gradient of nitrogen addition and then calculated the AMF phylogenetic alpha, beta and gamma diversity.