THE IMPACT OF FIRE ON SOME MEDITERRANEAN LAND SNAIL COMMUNITIES AND PATTERNS OF POST-FIRE RECOLONIZATION

Abstract

While several studies deal with the subject of the impact of fire on Mediterranean fauna and subsequent patterns of recolonization, the impact of fire on land snail communities has not yet been studied. Nevertheless, living in vegetation or in litter, land snails are highly sensitive to fire and thus constitute a good model to define the effects of fire on fauna. The aims of this study were to analyse the immediate and long-term impact of fire on the land snail communities and to reveal the patterns of post-fire recolonization within these communities. A stratified sampling scheme was carried out, throughout garrigues and forests of Provence (France), according to fire age and distances from the burned/unburned boundaries and from vegetation refuges. The data collected were studied using multivariate statistical analyses (Correspondence Analysis, Canonical Correspondence Analysis and Partial Canonical Correspondence Analysis). The main results do not agree with the original working hypotheses, i.e. land snail recolonization progressing from margins of the burned areas and from vegetation areas spared by the fire. The role of burned/unburned boundaries and vegetation refuges are not significant. Moreover, although land snail communities decrease in diversity and abundance, they are resilient to fire perturbation. In fact, one year after a fire all ecological groups are represented, which suggests a certain permanence within the malacological communities. Thus, the fire mosaic and landscape heterogeneity determine numerous scattered refuges that have proved to be difficult to locate. Finally, the composition of the post-fire land snail communities depends essentially on the habitat structure and, to a lesser degree, on their floristic composition and topography.