PNNL

Abstract

Bioenergy crops are a promising energy alternative to fossil fuels. The belowground input of bioenergy crop residues shape soil microbial community composition, which in turn influences nutrient cycling and plant productivity. In addition to cropping inputs, site characteristics (e.g. soil texture, climate) influence bacterial and fungal communities. We explored the response of soil microorganisms to bioenergy cropping system (switchgrass vs. maize) and site (sandy loam vs. silt loam) within two long-term experimental research stations using 16S and ITS amplicon sequencing of soil RNA and DNA which represent the live and total community respectively. Bacterial and fungal membership differed widely between live and total communities with more Proteobacteria and Glomeromycota present in live communities and more Verrucomicrobia and Ascomycota present in total communities. Specific highly abundant fungal taxa within live communities were indicative of site and cropping systems, providing insight into treatment-specific, agriculturally-relevant microbial taxa that are obscured within total community profiles. Glomeromycota spp. were solely indicative of switchgrass soils, while a few very abundant Mortierellomycota spp. were indicative of silty soils. Although live and total communities were compositionally different after long-term agricultural management, microbial responses to environmental parameters were consistent regardless of nucleic acid type (RNA vs. DNA). While a standard DNA-based analysis was sufficient for detecting a site effect, live and total communities differ in dominant membership reflecting both contemporary and time-integrated responses of complex soil microbiomes to environmental change.