Nitrogen fertilization alters belowground plant – microbe interactions in two Populus species

Background/Question/Methods

Environmental perturbations can lead to decreased plant growth and productivity leading to poor yields of bioenergy feedstock and crop plants. Studies have shown plant microbiomes may alleviate plant stress responses, thereby mitigating the severity of detrimental effects on plant growth under abiotic and biotic stress. Unraveling the interactions between plant hosts and microbes can result in novel uses of microorganisms to aid in plant health, productivity, and altering ecosystem functions like carbon sequestration and nitrogen (N) cycling. To approach this, we propagated Populus deltoides and P. trichocarpa with and without N fertilization using historical agriculture soils from Oregon and West Virginia, which had distinct chemical properties and initial soil microbial communities. In addition to the collection of plant phenotypic data, the root endosphere, and soil microbiome of all plants were characterized with amplicon sequencing.

Results/Conclusions

We found N fertilization had a pronounced effect on microbial diversity in both the fungal and bacterial communities with an increase diversity in the soil and decreased diversity in the root microbiomes. Additionally, N addition led to a decrease in Ectomycorrhizal (EcM) taxa in the root and soil microbiomes for both Populus species indicating a reduced importance of plant-microbe symbiosis when nutrient constraints are alleviated. However, Arbuscular Mycorrhizal (AM) fungal taxa increased in the roots of P. deltoides and decreased in the roots of P. trichocarpa. We also found that soil origin and host species were stronger indicators of bacterial and fungal microbial community structure. Together this demonstrates plant recruitment for microbes are determined by numerous abiotic factors that can be altered or enhanced with the addition of N depending on the host species.