Composition of Soil Viral and Bacterial Communities after Long-Term Tillage, Fertilization, and Cover Cropping Management

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Abstract
Soil bacterial communities are a critical component for stability and function of terrestrial ecosystems. Viruses are ubiquitous in soils and have significant impacts on the structure and functions of bacterial host communities. However, little is known about the variation of bacterial and viral communities and their connection under various land use management practices. In this study, we evaluated bacterial and viral diversity using 16s rRNA sequencing and RAPD-PCR, respectively, and estimated viral and bacterial abundances by enumeration method, and used structural equation model to reveal relationship between viruses, bacteria, and soil properties, in soils from a long-term conservation management experimental site in western Tennessee USA. Inorganic N fertilization, cover cropping, and tillage treatments showed no significant differences in bacterial alpha-diversity but significantly influenced the structure, as suggested by differences in beta-diversity of bacterial communities. Higher soil pH and water content were favorable to bacterial abundances. Cover cropping, soil water content, and bacterial abundances may explain the variation of viral abundances and community structure in soil. Structural equation modeling showed that bacterial abundances positively influenced viral abundances, and in turn virus abundances and bacterial alpha diversity affected the level of extractable dissolved organic C, which exerted a feedback effect on the structure of bacterial communities. This feedback loop suggests that viral lysates might significantly contribute to reshaping bacterial community structure and indirect influence bacterial alpha diversity. This supports the theory of the “viral shunt” in soil ecosystems. This study indicated that long-term conservation management can reshape soil bacterial and viral communities and influence their interactions in biogeochemical processes.

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