Mycorrhizal‐mediated nitrogen acquisition in switchgrass under elevated temperatures and N enrichment

Arbuscular mycorrhizal fungi ( AMF ) can perform key roles in ecosystem functioning through improving host nutrient acquisition. Nitrogen ( N ) is an essential nutrient for plant growth, however, anthropogenic N loading (e.g. crop fertilization and deposition from combustion sources) is increasing so that N now threatens ecosystem sustainability around the world by causing terrestrial and aquatic eutrophication and acidification. It is important to better understand the capacity of AMF to directly uptake N from soils and transfer it to host plants because this process may increase N recycling and retention within ecosystems. In addition to understanding the role of AMF in the N cycle in the present day it is important to understand how AMF function may change as global change proceeds. Currently the net effects of N enrichment and elevated temperature predicted with global change on AMF are unknown. In this study, we examined the effects of N enrichment by simulated N ‐deposition loading, elevated temperatures expected by future global changes and their interactions on growth and AMF ‐mediated N acquisition of switchgrass ( P anicum virgatum var. A lamo), an important species for biofuel production. Switchgrass plants were grown in microcosm units that divided mycorrhizal roots from AMF hyphae and organic residues enriched with 15 N by compartments separated by an air gap to reduce N diffusion. While AMF did not enhance switchgrass biomass, mycorrhizas significantly increased 15 N in shoots and total shoot N . Neither N enrichment nor elevated temperatures influenced this mycorrhizal‐mediated N uptake and transfer. Results from this study can aid in developing sustainable bioethanol and switchgrass production practices that are less reliant on synthetic fertilizers and more dependent on internal N recycling from AMF .