significance of a root-fungus association in two Carex species of high-alpine plant communities

The relationship between roots of Carex firma, C. sempervirens and their commonly occuring dark septate fungal associates was examined. Two typical fungal associates were isolated and reinoculated onto aseptically grown seedlings of the two host species. Both isolates produced significant increases of dry matter production in C. firma compared with uninoculated controls. No growth stimulation was obtained in C. sempervirens. Shoot phosphorus concentrations were significantly increased in both host species by inoculation. The absence of growth stimulation in C. sempervirens may be due to carbon drain imposed by the fungus or to the fact that nutrients other than phosphorus are growth limiting. The nature and possible ecological significance of the root-fungus association is discussed and it is suggested that the relationship is mutualistic rather than parasitic.