The diversity and occurrence of fungi on decomposing leaves in the terrestrial and aquatic environment were studied in summer (March, 1996) and winter (June, 1996) in three kinds of vegetation: Eucalyptus spp. forest, secondary forest, and an intermediate vegetation that covers "Ilha dos Eucaliptos", an island in Guarapiranga Reservoir, São Paulo, State of São Paulo. A total of 41 filamentous fungi (98 occurrences) were found through leaf disks washing technique followed by plating on culture media,of which 36 belonged to the mitosporic fungi group, four to Zygomycota and one to Ascomycota. Twenty eight taxa (37 occurrences) were registred for Eucalyptus spp. Forest, 21 taxa (33 occurrences) for the secondary forest, and 20 taxa (28 occurrences) for the intemediate vegetation. The submerged leaves supported more diversified mycota, composed of 35 taxa (58 ocurrences), whereas the mycota on the leaf litter were composed of 19 taxa (40 occurrences). The Index of Sorensen revealed the highest similarity (58.54%) between mycotas of the intermediate vegetation and secondary forest, followed by the mycotas of the intermediate vegetation and Eucalyptus spp. forest (54.17%). Mycotas of the Eucalyptus spp. forest and the secondary forest were the most different ones (similarity = 44.9%). Concomitantly to the submerged leaves collection some abiotic parameters were measured in the water, such as temperature at 10 cm deep, pH and dissolved oxygen content. The means were compared by variance analysis (ANOVA). In summer, the abiotic factors were significanly higher in the secondary forest than in the other sites. There is evidence that vegetation type and seasonal variations may act on the leaf decomposing fungi. Acccording to the results, the island studied offers conditions for the development of a diversified mycota, with high occurrence rate, thus being an ideal place for further studies on saprobiotic fungi in lentic systems.
Leaf litter decomposition; fungi; Eucalyptus; secondary forest
