Exogenous arbuscular mycorrhizal fungi increase soil organic carbon and change microbial community in poplar rhizosphere

Arbuscular mycorrhizal fungi (AMF) increase soil organic carbon (SOC) deposition via secretion of glomalin-related soil protein (GRSP) and modulation of plant carbon partition. Two exogenous AMF inocula (Rhizophagus irregularis and Glomus versiforme) were applied to the roots of Populus x canadensis seedlings grown in the unsterilized nursery soil. The diversity of fungal and bacterial communities was assessed by the polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) method, while the accumulation of GRSP and SOC content in 22.5 cm-deep soil was measured. The results indicated that two AMF additions increased root colonization frequency as well as poplar biomass, especially root biomass accumulation. Two AMF applications improved the easily extractable-GRSP, total-GRSP, and SOC accumulation in the rhizosphere of poplar seedlings, limited the fungal community, and exerted no influence on the bacterial community. The effect of G. versiforme on GRSP and SOC accumulation was higher than that of R. irregularis. The AMF introduced GRSP, and SOC accumulation was highly correlated the limited fungal species richness.