AbstractPlant and soil microbial diversity are linked through a range of interactions, including the exchange of carbon and nutrients but also herbivory and pathogenic effects. Over time, associations between plant communities and their soil microbiota may strengthen and become more specific, resulting in stronger associations between plant and soil microbial diversity. We tested this hypothesis in a 4-year long field experiment in which we factorially combined plant community history and soil legacy with plant diversity (1, 2, 4, 8, 60 species). Plant community history and soil legacy refer to the presence (“old”) or absence (“new”) of a common history of plants and soils in 52 different plant species compositions during 8 years in a long-term biodiversity experiment in Jena, Germany. After 4 years of growth, we took soil samples in the new field experiment and determined soil bacterial and fungal composition in terms of operational taxonomic units (OTUs) using 16S rRNA gene and ITS DNA sequencing. Plant community history did not affect overall soil community composition but differentially affected bacterial richness and abundances of specific bacteria taxa in association with particular plant species compositions. Soil legacy markedly increased soil bacterial richness and evenness and decreased fungal evenness. Soil fungal richness increased with plant species richness, regardless of plant community history or soil legacy, with the strongest difference between plant monocultures and mixtures. Particular plant species compositions and functional groups were associated with particular bacterial and fungal community compositions. Grasses increased and legumes decreased fungal richness and evenness. Our findings indicate that as experimental ecosystems varying in plant diversity develop over 8 years, plant species associate with specific soil microbial taxa. This can have long-lasting effects on belowground community composition in re-assembled plant communities, as reflected in strong soil legacy signals still visible after 4 years of growing new plant communities. Effects of plant community history on soil communities are subtle and may take longer to fully develop.
Abiotic and Biotic Soil Legacy Effects of Plant Diversity on Plant Performance
