Relationship between environmental factors and the proportions of fungal trophic groups in forest ecosystems of the central Mediterranean area

Forest decline has recently been observed in many parts of Europe. Myco ̄ora, especially symbionts, has been reported to decrease 5±10 years before the forest community begins to decline. Mycological research can therefore be useful for forecasting the evolution of forests subject to man-made stress. Researchers in central Europe have found that the mycorrhizal ratio (percentage of mycorrhizal fungi with respect to all macromycetes) is a useful index of the level of forest pollution, being much lower in contaminated areas. Here, data on macromycetes of different forest ecosystems from central Italy were examined to determine whether this index is applicable to the Mediterranean area, and to determine whether factors other than atmospheric pollution could in ̄uence the mycorrhizal ratio in these situations. The results show that the percentage, and especially the number of mycorrhizal fungi, was signi®cantly correlated with environmental parameters such as altitude, number of tree species and tree cover. It is concluded that in the Mediterranean area a low mycorrhizal ratio does not always indicate that a forest is subject to air pollution