Phytosociological and ecological features of a dying-back reed bed at the Lake Trasimeno (central Italy)

Common reed die-back is a well known phenomenon in Central Europe, recently detected also at the Lake Trasimeno in Central Italy. Floristic and vegetational traits of declining and healty reed stands have been taken into account, in the same area, and analysed from a phytosociological point of view. Results show that Phragmites australis tends to form monospecific stands in permanently flooded areas rich in organic deposits and autogenous litter, where the symptoms of reed decline seems to be more severe. Species rich stands develop in terrestrial areas, on nutrient-rich soils, where reed shows vigorous growth and healthy condition; however, the observed floristic richness is mostly due to invasive and nitrophylous species from the classes Stellarietea and Artemisietea, which originate a ‘pseudo-reed bed’, lacking in typical palustrine species. The results draw attention, also in southern Europe, to the risk of loss of an ecosystem which plays an important role in biodiversity conservation.