Effect of plant communities on bacterial and fungal communities in a Central European grassland.

BACKGROUND: Grasslands provide fundamental ecosystem services that are supported by their plant diversity. However, the importance of plant taxonomic diversity for the diversity of other taxa in grasslands remains poorly understood. Here, we studied the associations between plant communities, soil chemistry and soil microbiome in a wooded meadow of Certoryje (White Carpathians, Czech Republic), a European hotspot of plant species diversity. RESULTS: High plant diversity was associated with treeless grassland areas with high primary productivity and high contents of soil nitrogen and organic carbon. In contrast, low plant diversity occurred in grasslands near solitary trees and forest edges. Fungal communities differed between low-diversity and high-diversity grasslands more strongly than bacterial communities, while the difference in arbuscular mycorrhizal fungi (AMF) depended on their location in soil versus plant roots. Compared to grasslands with low plant diversity, high-diversity plant communities had a higher diversity of fungi including soil AMF, a different fungal and soil AMF community composition and higher bacterial and soil AMF biomass. Root AMF composition differed only slightly between grasslands with low and high plant diversity. Trees dominated the belowground plant community in low-diversity grasslands, which influenced microbial diversity and composition. CONCLUSIONS: The determinants of microbiome abundance and composition in grasslands are complex. Soil chemistry mainly influenced bacterial communities, while plant community type mainly affected fungal (including AMF) communities. Further studies on the functional roles of microbial communities are needed to understand plant-soil-microbe interactions and their involvement in grassland ecosystem services.

Diversity of fungi and bacteria in species-rich grasslands increases with plant diversity in shoots but not in roots and soil.

Microbial communities in roots and shoots of plants and in soil are important for plant growth and health and take part in important ecosystem processes. Therefore, understanding the factors that affect their diversity is important. We have analyzed fungal and bacterial communities associated with plant shoots, roots and soil over a 1 km2 area in a semi-natural temperate grassland with 1-43 plant species per 0.1 m2, to describe the relationships between plant and microbial diversity and to identify the drivers of bacterial and fungal community composition. Microbial community composition differed between shoots, roots and soil. While both fungal and bacterial species richness in shoots increased with plant species richness, no correlation was found between plant and microbial diversity in roots and soil. Chemistry was a significant predictor of bacterial and fungal community composition in soil as was also the spatial location of the sampled site. In this species-rich grassland, the effects of plants on the microbiome composition seemed to be restricted to the shoot-associated taxa; in contrast, the microbiomes of roots or soil were not affected. The results support our hypothesis that the effect of plants on the microbiome composition decreases from shoots to roots and soil.