Analisi dei processi di rinaturalizzazione nei vigneti e cappereti abbandonati del paesaggio terrazzato di Pantelleria (Canale di Sicilia)

This study analyses the vegetation dynamics in the terrace landscape of Pantelleria Island (Sicilian Channel). The main questions were to determine the sequence of plant communities in time and to find out which environmental factors influence the course and the speed of succession. In the thermomediterranean part of the island were made vegetation relevés in five different fallow age classes, investigating three different ecological subunits: the terrace surface, the wall base and the wall in North-facing as well as in South-facing vine and caper fallows. The results show that undisturbed abandoned terraces are subject to rapid renaturation: 50 to 80 years old fallows are covered by dense maquis communities. Succession proceeds more slowly in South-facing fallows than in North-facing ones, but, from a structural and floristic point of view, both arrive at similar final stages and seem to have a Quercus ilex wood as the climax community. Ordination techniques (DCA and CCA) revealed that the fallow age, the exposition and the presence of safe sites are the most influential environmental factors. The safe sites, provided by the former crop plants, mitigate temperature extremes and wind intensity during the first stages of succession. The predictable sequence of plant communities in the course of succession can be interrupted by a few species able to form almost monospecific stands. These are Cistus sp. pl., known to show enhanced germination from seed bank after fire, or clonal species such as Rubus ulmifolius, Andropogon distachyon and Hyparrhenia hirta. The highest values of species richness are recorded in the first years after abandonment, when environmental factors are very heterogeneous, while the lowest ones are typical of the oldest fallows.