Two grass species fail to display differing species-specific effects on soil bacterial community structures after one season of greenhouse growth

Background and aims Plant impacts on soil microbial community composition and function are believed to be important but remain poorly understood. We looked at thebacterialcommunityeffectsofgrowingtwodifferent plant species in soils with differing plant growth histories. Methods Big bluestem (Andropogon gerardii: Ag) and cereal rye (Secale cereale: Sc) plants were grown in six soils with different planting and management histories for 14 weeks in a greenhouse study. Both prior to planting and harvesting, soil was collected for analysis. Bacterial community DNA was extracted and analyzed via 454 pyrosequencing and soil edaphic characteristics were also measured. Results Significant shifts in composition were observed between pre-plant and post-plant bacterial communities in 23 of the 40 most abundant orders but only one order (Nitrospirales) differed significantly between the two plant species treatments (Ag vs. Sc). Compared to preplant communities, post-plant communities increased significantly in alpha diversity (within community) but exhibited an overall decrease in beta diversity (between community), indicating that soil communities became more similar after growth of either Ag or Sc. Soil pH was the strongest predictor of bacterial community ordination, followed by percent carbon, organic matter, phosphorous, nitrogen, and potassium. Conclusions Overall, the relative lack of significant differences between the soil bacterial communities of Ag- and Sc-planted soils suggests that potential plantspecies-specific effects are strongly modulated by growth conditions and edaphic soil characteristics.