Do fungal leaf-symbionts affect grass litter decomposition? A microcosm approach using Lolium multiflorum

OMACINI M., E.J. CHANETON, P. OTERO, C.M. GHERSA

OIKOS

Nordic ecological society

Lugar: Lund; Año: 2004 vol. 104 p. 581 - 590

0030-1299

Infection with symbiotic fungal endophytes has been reported to decrease herbivory in several temperate grasses. We tested the hypothesis that foliar endophytes of grasses may also affect belowground processes upon their host death, by altering the litter quality for detritivores or the microenvironment for decomposition. Microcosm-litterbag experiments were used to assess decay rates for litter produced by endophyte (Neotyphodium sp) infected vs. uninfected Lolium multiflorum populations, and to examine endophyte-mediated effects of prior site occupants on current litter decomposition. We found that litter from endophyte-infected L. multiflorum decomposed more slowly than litter from endophyte-free conspecifics and from a naturally uninfected grass, Bromus unioloides. The endophyte-grass association also modified the decomposition environment, so that B. unioloides litter decomposed faster when placed underneath a thick layer of endophyte-free L. multiflorum litter. Litter decay rates increased with the amount of root debris remaining in situ from the previous season, but were not influenced by the infection status of prior site occupants. The reduced decomposability of litter from infected L. multiflorum plants persisted across a range of microenvironments defined by different amounts of aboveground litter and soil moisture conditions. Endophyte infection tended to reduce the N concentration of decaying litter; however, litter N content and C/N ratio mainly accounted for interspecific differences in decomposition. Other changes in litter chemistry, perhaps leaching of fungal alkaloids, might contribute to alter soil decomposer activity in the presence of litter deposited by endophyte-infected grasses. Our results imply that fungal endophytes not only can affect herbivory food chains, but also soil organisms and the ecosystem processes they regulate. This study suggests a novel role for symbiotic foliar endophytes in linking aboveground and belowground subsystems.