Multitemporal floristic analysis on a humid area in Rome's archaeological site as indicator for environmental change.

A multitemporal analysis on a humid area in Rome's archaeological site is presented; the floristic data are used as bioindicators for main environmental changes over the last 50 years. By comparing the structural, biogeographical and ecological features of today's florula with the ones of a 1955 survey, and by assessing the new, the rare and the locally disappeared species, it was possible to define and analyse the main floristic changes and their ecological meaning for this site. Our results show that the floristic richness of the area did not differ significantly from 1955. However, the species composition has changed considerably: over 40% of the species have disappeared. More than half of these were rare and typical of humid environments. Approximately the same number of species has appeared but these are mainly ruderal and widespread entities, with the overall result being a progressive and general vulgarization of the local flora. Finally, we analyse the main reasons, linked for the most part to human activities, which led to the reported floristic changes.