COS 186-1 - CANCELLED - Novel fungal endophyte infection impacts grassland greenhouse gas emissions under climate stressors

Background/Question/Methods

Plant-microbe interactions, such as tall fescue (Schendonorus arundinaceus) and fungal endophyte (Epichloë coenophiala), can affect ecosystem response to perturbations, including changing rainfall patterns and increasing temperatures associated with climate change. Tall fescue infected with the wild-type (common toxic) strain of E. coenophiala often exhibits improved tolerance to environmental stresses and modified soil greenhouse gas (GHG) fluxes compared to endophyte-free stands. Because the wild-type E. coenophiala strain produces alkaloids which negatively impact grazing animals, release of new cultivars with novel endophyte strains that lack the ability to produce mammal-toxic alkaloids has become common. It is unknown if differing novel endophyte strains confers differing levels of environmental resistance or reduction of soil GHG flux. This study quantified the impact of fescue-fungal symbioses on GHG flux in response to increased temperature and altered water availability over two years in Lexington, KY (USA). Twenty plots were randomly arranged in five blocks with four climate treatments: ambient control, +3 °C heat, altered precipitation (less frequent, more intense), and combined heat and altered precipitation. Two cultivars with/without endophyte symbionts were used: Jesup MaxQ (novel AR542) and Texoma MaxQ II (novel AR584). Ammonia (NH₃), nitrous oxide (N₂O), and carbon dioxide (CO₂) flux was measured biweekly.

Results/Conclusions

In 2016, endophyte-infection decreased CO₂ flux (p = 0.03) without a significant endophyte*cultivar interaction (p = 0.4). NH₃ flux varied with endophyte*cultivar interaction (p = 0.01) in which endophyte-infection increased NH3 flux for Texoma but not Jesup. NH₃
flux increased with increased temperature (p = 0.003). N₂O flux differed by endophyte*cultivar (p = 0.01) in which endophyte infection decreased flux for Jesup but increased flux for Texoma. In 2017, CO₂ flux differed by precipitation*endophyte interaction (p = 0.007). Endophyte-infection reduced CO₂ flux with decreased precipitation. Endophyte infection resulted in no difference in NH₃ (p = 0.56) or N₂O flux (p = 0.25) in 2017. However, NH₃ flux increased with decreased water availability (p = 0.02). These results suggest novel endophytes reduce CO₂ flux in changing climatic scenarios. Variance in N₂O and NH₃ flux with year and endophytic infection warrants more study for the development of cultivars capable of reducing GHG emissions.