Arbuscular mycorrhiza fungi increase soil denitrifier abundance relating to vegetation community

Denitrification by microorganisms in soil regulates ecosystem nitrogen availability and cycling. Although arbuscular mycorrhiza fungi (AMF) are best known as the key connectors between plant and microorganisms in below-ground soil, however, less knowledge is available about the interactive effects of AMF and vegetation community traits on soil denitrifiers. In this study, we manipulated experimental pots with or without AMF inoculation (AMF+ and AMF− treatments) under three plant richness levels and 27 different plant community compositions. Our results provided evidence that inoculation of AMF significantly increased the abundances of nirS-, nirK- and nosZ-type denitrifiers as revealed by quantitative PCR (qPCR), which inferred a positive role of AMF in N-cycling microorganisms. Plant community traits, including richness, community composition, biomass and species, were less important in influencing the abundances of soil denitrifiers, and no significant interactive effect was detected between AMF inoculation and plant richness or plant community compositions, indicating a weak direct relationship between plants and soil denitrifiers. Our study provided comprehensive insights into the roles of AMF-plant associate bio-system in driving the variation of soil denitrifiers.