Severance of arbuscular mycorrhizal fungal mycelial networks in restoration grasslands enhances seedling biomass

Establishment and growth of grassland plant species is generally promoted by arbuscular mycorrhizal fungi (AMF) when grown in isolation. However, in grassland communities AMF form networks that may connect individual plants of different ages within and between species. Here, we use an ingrowth core approach to examine how mycorrhizal networks influences performance of seedlings in grasslands. We selected four grass and four forb species with known negative or neutral-positive plant–soil feedback and grew them individually in steel mesh cores filled with living field soil. Cores were placed in six restored grasslands, three grasslands were of relatively young and three were of older successional age. Ingrowing mycorrhizal fungal hyphae were severed twice a week in half of all cores, which resulted into reduced AMF colonization and increased seedling biomass, irrespective of the fields' succession stage, and the plants' grass/forb group, or plant–soil feedback type. In the control cores, root colonization by AMF was negatively correlated to seedling biomass, whereas there was no such relationships in the cores that had been lifted. We conclude that connections to arbuscular mycorrhizal networks of surrounding plants had a negative impact on biomass of establishing forb and grass seedlings.