LAUSR

Purpose-grown biomass is derived from herbaceous species such as switchgrass ( Panicum virgatum ), and miscanthus ( Miscanthus giganteus ) as well as woody species such as poplar ( Populus spp.) and willow ( Salix spp.). Feedstocks derived from these crops are used in the production of biofuels. Soil microorganisms in biomass cropping systems play important roles in soil fertility, nutrient cycling, and plant productivity. However, they can be influenced by plant species and management practices. This study assessed the distribution and abundance of soil microbial communities (total bacteria, total fungi and arbuscular mycorrhizal fungi (AMF) as influenced by poplar and willow (woody biomass crops) and switchgrass and miscanthus (herbaceous biomass crops) planted in fertilized and unfertilized plots in marginal soils. Soil was sampled in the fall of 2014 and spring of 2015 from biomass crops planted on marginal land in Guelph, Ontario, Canada. DNA was extracted, and quantitative PCR was used to enumerate the total bacteria (16S rRNA), total fungi (ITS), and AMF (AMF SSU rRNA) abundance in the soil. The total fungi and AMF abundance differed significantly across the herbaceous and woody species, with higher fungal abundance in the poplar resulting in higher fungal/bacterial (F/B) ratios compared to switchgrass and miscanthus. However, AMF were more abundant in the herbaceous species than in the woody species. Fertilization had a positive effect on the bacterial and fungal communities but not the AMF community under the different biomass cropping systems assessed in the fall season. These results illustrate that biomass crop species and management practices in biofuel cropping systems strongly influence soil microbial communities.