Plant and soil controls on mycorrhizal fungal communities

Populations of vesicular-arbuscular mycorrhizal (VAM) fungal spores were studied in 4-yr-old monocultures of five successional grass species grown in a gradient of soil mixtures ranging from pure subsurface sand to pure sandy loam topsoil; 19 species of VAM fungi were found across all treatments. Of the 12 most abundant VAM species, six had a significant dependence on both soil mixture and host species, while two were dependent only on soil and two only on host. These are the first results indicating that even closely related hosts (five grasses) may cause divergence in VAM fungal communities on initially identical soils. The fungal communities in the two late successional grasses were most similar to one another and least similar to the fungal communities in the early successional grass species. Cluster analysis of the similarity of fungal communities by soil mixutre showed the fungal communities in the sandy end of the soil gradient diverged predictably from the fungal communities in the black soil end of the gradient. Soil factors and plant species may be of equal importance in regulating the species composition of VAM fungal communities. -from Authors