Competition Between Tall Fescue and Plantago Under Elevated Atmospheric CO2: Impact of Endophytic Fungi and Mineral N Inputs.

Tall fescue (Festuca arundinacea Schreb) is one of the most important perennial grasses as forage and turfgrass. It is usually associated with a systemic endophytic fungus (Neotyphodium coenophialum Morgan-Jones and Gams). The endophytic fungus often increases the host resistance to stresses, thus enhancing competitiveness. Because endophytic fungi produce alkaloid toxins that are harmful to animals, endophyte-free or toxin-free tall fescue cultivars have recently been developed and planted in forage grasslands. However, it is unknown whether this alters the competitiveness of tall fescue against other weeds such as plantago species and how the climate change factors will affect these interactions. We examined how CO₂ enrichment and N availability affect the interactions between plantago (Plantago lanceolata L.) and endophyte-infected (Jesup E+) and endophyte-free (Jesup E–) fescues. Two CO₂ levels (ambient and ambient+330 µmol mol^–1) and two N levels (10 and 35 mg kg^–1) were designed. Elevated CO₂ stimulated the growth of plantago greater than that of fescue, increasing the shoot biomass ratios of plantago to fescue. However, high N favored tall fescue over plantago. Plantago grew better in the presence of E+ than E- tall fescues, but this difference was reduced under elevated CO₂ and N inputs. These results suggest that the absence of endophytes may have limited effects on the competitiveness of tall fescue, and moderate N inputs could effectively help tall fescue compete its weedy competitors in forage systems.