Ecological trends in travertine colonisation by pioneer algae and plant communities

The distribution and amount of biological colonisation on the “Lungotevere” walls (Rome) were analysed to assess the ecological role of the main environmental parameters (solar irradiation, rain winds, prevailing winds) and of the nearby tree covering. The floral data indicate a close similarity of species in the stations examined and a dominance of Chroococcus lithophilus Ercegovic among the cyanobacteria and of Erigeron karvinskianus DC among the vascular plants. In these very hard conditions the exposure and amount of the water input do not seem to influence the flora qualitatively as much as it does quantitatively. The low value of microflora, as found in areas characterised by the presence of trees, can be referred to as resulting from the “umbrella” effect of the plants. The macroflora is less influenced by such effects due to the greater capacity of these plants to derive moisture through their roots.