Symbiosis with endophyte leads to greater C accumulation in grassland soils

Epichloë coenophiala forms aboveground symbiotic relationships with tall fescue (Festuca arundinacea) and provides the host with better fitness. This study investigated the effects of endophyte symbiosis on carbon mineralization in soil. Two soils were amended with endophyte-infected (E+) or endophyte-free (E−) residues of two tall fescue genotypes. At the end of the experiment, CO₂ evolution rates were monitored to quantify the mineralized carbon. The indices of carbon mineralization were significantly greater (LSD, P < 0.05) in the E−compared to E+ plant residue treated soils. Cellulose, hemicellulose, lignin contents, C:N and lignin:N ratios were significantly greater (LSD, P < 0.05) in soils with the E⁺ residues than in those with E⁻ residues. Additionally, the E+ plant residues consistently contained significantly less N (LSD, P < 0.05). Overall, it is concluded that grass-endophyte symbiosis results in the production of less biodegradable plant residues, in turn reducing the residue biodegradability and promoting greater C accumulation in the soils.