Management effects on temporal and spatial variations in temperate grassland microbiomes
Background: Leaf and root-associated microbial communities play crucial roles in plant health, yet the factors that govern microbiome assembly and dynamics are still poorly understood. Through the study of the grass species Agrostis capillaris at a trophic rewilding site in Mols Bjerge National Park in Denmark, we aimed to characterize the dynamic of fungal and bacterial communities associated with leaves and roots, over three consecutive years using amplicon sequencing. We collected samples from plants subjected to different experimental vegetation management practices: autumn mowing with removal of biomass, all-year horse and cattle grazing and permanent exclosure with passive succession. Results: We identified very different communities of bacteria and fungi associated with leaves and roots of A. capillaris, reflecting the selective forces of distinct plant tissue. Over the three years, bacterial communities were highly stable, while fungal communities showed significant variation in the composition of taxa. Intriguingly, we observe significant differences in the microbial diversity and composition across the different vegetation management practices whereby mowing, over time, prevents an increase in bacterial diversity. In addition, the in-depth community sequencing allowed us to predict positive and negative interactions of microbial species and to identify distinct hub species in plots with grazing, mowing and passive succession.  Conclusions: Our study provides evidence for different dynamics of bacterial and fungal communities associated with an abundant grass species. Moreover, the results suggest that the vegetation management practices, especially mowing, can constrain microbial diversity, which may have downstream consequences for plant health.