Long-term nitrogen fertilization alters phylogenetic structure of arbuscular mycorrhizal fungal community in plant roots across fine spatial scales

Purpose Nitrogen enrichment is known to have a substantial impact on arbuscular mycorrhizal fungal (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, remained poorly understood. Methods We collected 256 root samples of 16 common plant species belonging to 8 families along a nitrogen addition gradient (0, 5, 10 and 15 g N m(- 2) year(- 1)) and then calculated the AMF phylogenetic diversity and dispersion across fine spatial scales using the next-generation sequencing. Results Nitrogen addition and host identity significantly affected the phylogenetic alpha dispersion (plot-level phylogenetic dispersion), 'within-treatment' phylogenetic beta dispersion (phylogenetic dispersion among replicate plots within each treatment) and phylogenetic gamma dispersion (treatment-level phylogenetic dispersion), which were caused by the decrease in the relative abundance of a dominant genus (Glomus) and the increase of several non-dominant genera. Furthermore, nitrogen addition affected phylogenetic alpha dispersion mainly by influencing soil properties. In addition to the direct effect on 'within-treatment' phylogenetic beta dispersion, nitrogen addition and plot distance also significantly increased the dissimilarity of plant community and soil environments, thereby resulting in an increase in phylogenetic beta dispersion ultimately. Conclusion The deterministic environmental filtering (host identity and soil environment) and short-distance dispersal limitation played critical roles in AMF community assembly under nitrogen fertilization conditions. Insightfully, this study provides a mechanistic understanding of the response of AMF community to nitrogen addition across fine spatial scales.