Changes in microfungi and fauna of burned and unburned soils in a Mediterranean area of southern Italy

The effect of experimental fires on fungi and fungivorous microarthropods was investigated in a coastal area of southern Italy. In particular, in burned soils affected by different severity fires (low and high) the following parameters were determined at 245 (March 2001), 364 (July 2001) and 728 (July 2002) days after fire: total and active fungal mycelium, abundance and species density of total, xerotolerant and heat-stimulated fungi as well as abundance and species density of oribatid mites and springtails, which are the main groups of mesofauna. Fungal mycelium decreased in burned soils, compared to unburned soils, during the whole study period (active mycelium) or only at 728 days after fire (total mycelium), with significant effect of fire severity only at 245 days after fire. Similarly, species density of total mycobiota tend to be reduced in burned soils; by contrast, total mycobiota abundance increased in burned soils, reflecting the increase in abundance of xerotolerant and heat-stimulated fungi. To some extent total fungal decrease could be responsible for reduction in abundance and species density of oribatid mites and springtails often occurred in this study (with the exception for July 2002), particularly in soils affected by high-severity fire. In fact, positive correlations between faunal and fungal parameters were often observed. However, the effect of other factors on soil fauna cannot be excluded. A clear temporal dynamics of considered biological parameters was generally evident, with the lowest values in the first summer after fire (July 2001), characterized by the lowest soil water content. In fact, positive correlations with soil water content were found for fungal mycelium and abundance as well as for springtail species density. Different organism groups showed the highest abundance and species density in different times (at March 2001 or July 2002). Data suggest that changes due to fire together with seasonal variation of climatic factors (probably emphasized by fire) raise the survival probability of several species, also providing temporary refuges to species (such as heat-stimulated fungi) that are unable to compete in undisturbed soils, so that different groups were favoured in different microhabitats and/or in different times.