Arbuscular mycorrhizal fungal-mediated reductions in N2O emissions were not impacted by experimental warming for two common pasture species

Soil emissions of nitrous oxide (N2O), a potent greenhouse gas associated with agricultural systems, can be reduced by the activity of arbuscular mycorrhizal (AM) fungi. It is unclear, however, whether climate change may impact this ecosystem service provided by AM fungi. To assess the extent that warming may affect AM fungal mediation of N2O emissions from pastures, we grew lucerne (Medicago sativa, also called alfalfa) and tall fescue (Festuca arundinacea) under ambient (aT) and elevated (eT) temperature (+4 °C) regimes in the presence or absence of the AM fungus Rhizophagus irregularis. N2O emissions were measured from pots at five timepoints over a four-month period, while total plant biomass, nitrogen, phosphorus and mycorrhizal parameters (root length colonised and extraradical hyphal biomass in soil) were measured following a final destructive harvest. For both species, AM fungi significantly reduced N2O fluxes to a similar extent under both temperatures. The N2O reduction due to AM fungal inoculation was not influenced by warming. Overall, AM fungi were shown to reduce N2O emissions under current and predicted future warming scenarios for these two common pasture species, highlighting the role of microbial symbionts in mediating terrestrial feedbacks to future climate change.