Arbuscular mycorrhizal (AM) fungi contribute to soil organic carbon storage in restored grasslands by increasing carbon flow into soil and, potentially, through glomalin-related soil protein (GRSP) production. However, increased soil phosphorus can disrupt the AM-plant mutualism, resulting in a shift to a less mutualistic AM fungal community. The objective of this study was to determine whether variation in phosphorous among restored prairies altered the mutualistic quality of AM fungi and other soil microbes and impacted the AM-mediated soil carbon storage pathway. Variation in soil phosphorus among restored prairies did not explain differences in GRSP or standing soil organic carbon stocks. Plant biomass and nutrient content increased as P content at the site of inoculum source increased despite reduced arbuscule colonization. Additionally, AM fungi were not necessary for GRSP production. My study suggests that elevated phosphorous in restored grasslands does not necessarily inhibit AM fungal mediated mechanisms of soil carbon storage.