Plant communities and soil properties mediate agricultural land use impacts on arbuscular mycorrhizal fungi in the Mixed Prairie ecoregion of the North American Great Plains

Arbuscular mycorrhizal (AM) fungi play an important role in the functioning and sustainability of agroecosystems, but they are also susceptible to changes in land use. The objective of this study was to determine the impact of agricultural land use practices on AM fungal communities and identify the factors that drive their assembly in the Mixed Prairie ecoregion of the North American Great Plains. Soil samples were collected from the four dominant agricultural land use types in this region (annual cropping, native grassland, tame grassland, and roadside ditches) at five locations and at three soil depths (0-15, 15-30, and 30-60 cm). The diversity and composition of the AM fungal communities were assessed using high throughput sequencing (454 pyrosequencing). We found that land use type significantly influenced the diversity and composition of the AM fungal communities. Annual cropland had the lowest diversity and a distinct community composition compared to the other land use types. This effect was most pronounced in the upper soil depth (0-15 cm), but was still evident in the lower depths (15-30 and 30-60 cm). Further analysis found a trend for AM fungal communities at lower soil depths to be a nested subset of communities in the top soil depth. Structural equation modeling revealed that land use affected AM fungal communities indirectly through the modification of plant communities and soil properties.