Fire effects on species-abundance distributions of soil fungal communities of Mediterranean maquis (southern Italy)

Fire is recognized as an important disturbance event in such ecosystems as temperate forest and Mediterranean maquis. The effects of fire on soil microbiota are determined by fire type, intensity, frequency and season of burning. The microbiota is a critical agent in relation to soil fertility and plant growth, due to its participation in nutrient cycling and in the formation and stabilization of soil aggregates. For soil fungi, fire, together with the concomitant combustion of soil litter, causes a decrease in the heterogeneity of the habitat as well as a decrease of fungal abundance and species numbers. The modification of the floristic composition and functioning of microfungal community lead to a subsequent new situation in competitive advantage of different parts of community. This research was carried out within the Project "Fire in Mediterranean environment: effects on vegetation and soil", supported by Italian Ministero dell’Università e della Ricerca Scientifica e Tecnologica. The focus of the present study was to determine how abundance and distribution of soil microfungal species were affected by two different intensities of burnings in Mediterranean maquis. Experimental fires, characterized by high and low intensity were performed during the summer (3 July 2000) in the "Castel Volturno Nature Reserve", a coastal area in southern Italy. The research was carried out in three sets of plots each one divided into three plots of 5x10 m. A control plot and a high and low intensity burned plot were performed for each group. Soil samples were collected under Phillyrea angustifolia L., at 0-5 cm depth, 7, 84, 147, 245, 364 and 727 days after the experimental fire. The soil samples were sieved through a 2 mm mesh-sieve and treated according to the soil dilution plate method (soil/water ratio 1:1000) to isolate the total mycoflora and xerophilic fungi; the heat stimulated fungi were selectively isolated by the dilution method through a thermal stimulation of the soil suspension. The usefulness of species-abundance data to examine the effects of disturbance have been documented in several cases and this approach is here utilized. The species abundance distribution models, obtained by the statistical analyses, have provided information on resource-partitioning among fungal species in the communities and on changes in the community structures over time.