Plants are generally known to influence belowground community composition and biodiversity of bacteria and fungi. It is also widely assumed that plant diversity promotes belowground diversity, however, little is known about the role of plant species versus functional groups (FGs) in steering composition and biodiversity of soil microbiota. We expect that there will be a hierarchy of factors influencing soil biodiversity: regionally, abiotic conditions such as climate and soil type will be key drivers, whereas locally, within areas of the same land use or agricultural practices, biotic factors such as plant inputs of root exudates and litter are most likely driving soil microbial community composition and its biodiversity. In order to test the contribution of plant species and plant FGs as drivers of local microbial community composition and diversity, we analysed the soil microbial community composition in the long-term biodiversity experiment at Jena, Germany. We used 454-pyrosequencing to examine and compare responses of bacteria, fungi and arbuscular mycorrhizal fungi (AMF) to plant species richness and composition. Plant diversities ranged from 1 to 16 sown plant species, and plant communities were composed of different species from a pool of 60.
Results/Conclusions
Richness (α-diversity) of soil fungi marginally increased with plant species richness, whereas there was no significant response of bacterial α-diversity. Similarity (β-diversity) of bacterial and fungal communities was not influenced by plant species richness, however, our analysis showed that plant functional groups had an effect on belowground biodiversity. Grasses and tall herbs had the highest α-diversity of bacteria, whereas that of legumes was lowest. Legumes had a different AMF community composition than non-legumes. On the other hand, there was no FG effect on α- and β -diversity of non-AM fungi. Variations in soil abiotic conditions across the 10 ha field experimental site turned out to have a major effect on soil microbial community composition. The community composition of soil bacteria across the entire field could be explained by soil texture, soil porosity and plant phosphorus content, whereas soil fungal community composition could be explained by soil structure, plant nitrogen, carbon and potassium contents, and plant productivity. Community composition of AMF was related to soil organic matter, silt, plant P, and legume cover. We conclude that across the Jena plant biodiversity experiment, overall composition of soil bacterial, fungal and AMF communities was influenced more by plant functional groups, plant nutrient content, and soil structure than by plant species richness.