Functional diversity of fungal assemblages decomposing the leaf litter of a natural mediterranean environment

Saprotrophic fungi have a wide range of important ecological functions associated with nutrients and carbon cycling processes in leaf litter and soil. Functional diversity of some strains of filamentous fungi associated to leaf litter decay in the Mediterranean maquis was analysed and compared by means of BiologTM FF microplates. The aim of the study is the evaluation of the relationship between the potential activity showed by pure fungal isolates (in vitro) and their actual ecological role in the field. Fungal frequencies and occurrence during the trophic succession on the natural resource were studied and used as key for understanding the metabolic profiles obtained in vitro. This approach can clarify the role of some key fungal species in the decomposition process within natural ecosystems. The study was carried out in the Natural Reserve of Castel Volturno (Southern Italy) where litter bags of pure and mixed leaves of low maquis plant species were incubated in one-year field experiment. Fungal species were isolated from decaying leaves and identified. Many species were not easy to be isolated in fact their reproductive structures have a close physical relationship with the natural substrate. Thirteen of these fungal isolates (including Beltrania querna Harkn, B. rhombica Penz. and Circinotrichum maculiforme Nees.) were selected being representative of the relevant fungal community. Three categories of occurrence frequencies were used to group the fungal species. Moreover, three different sampling times were considered. Assemblages of fungal species based on their natural occurrence in the field were compared with their potential metabolic abilities by means of multivariate statistical analysis (Discriminant Analysis and ANOVA). Results showed that fungi, during the trophic successions, occurred on the natural resource with a frequency that was strongly related to their metabolic profile as expressed in vitro with Biolog FF plates. Fungi replaced one another on the natural substrate in space and time, and the relative abundances of each species changed together with the potential ability of utilising particular clusters of substrates. The possibility of utilizing different spatial and temporal trophic niches driven by succession give a likely explanation of the positive effects that an apparent redundance of fungal species can have on leaf litter decomposition.