N-fertilizer-driven association between the arbuscular mycorrhizal fungal community and diazotrophic community impacts wheat yield

Nitrogen is a macronutrient which plays an important role in the net primary productivity of terrestrial ecosystems, and is critical to understand how nitrogen addition affects above- and below-ground organisms. However, direct and indirect interactions between microbial species response to nitrogen addition for wheat growth are still unclear. In this study, arbuscular mycorrhizal fungi (AMF) and diazotrophs (nifH gene) were selected as two groups of key functional microbes in wheat soil to investigate the comprehensive impact of diversity and community structures between them on wheat yield under a nitrogen gradient. Nitrogen addition resulted in a significant shift in AMF and nifH phylogenetic diversity and community structure. The interactions among AMF and nifH species were diminished in high N-treated soils compared to those in low N-treated soils. Structural equation model analysis showed that AMF community structure affected wheat yield directly, however, which was influenced by AMF diversity, diazotrophic diversity and community structure indirectly. The comprehensive effects of AMF and diazotrophs on wheat productivity indicated the importance of soil functional microbes as drivers for farmland ecosystem and plant growth. These results could be useful in understanding soil nutrient cycling and may help improve the mechanistic understanding of the tripartite interaction among nitrogen addition, microbes and wheat productivity.