Main ecological parameters affecting the colonization of higher plants in the biodeterioration of stone embankments of Lungotevere (Rome)

This study analyses the plant colonization of the stone embankments along the Tiber River (the Lungotevere) in relation to changes of lithotype (travertine, tuff, cement), inclination (80°, 60°, 45°), stone size, and exposure. The surveys of plant communities were carried out according to the phytosociological method and considering the variability of the ecological conditions. The vegetation data were analyzed using multivariate statistical analysis (cluster analysis) in order to highlight the affinity among the various groups of sampling areas. The ecological features of the vegetation, according to Ellenberg indicator values, were considered for the ecological interpretation. Results showed that many environmental factors interact in giving rise to a differential plant cover and species richness, but that some are more relevant than others, such as the lithotype nature, especially in relation to the differential stone porosity. Also, changes in inclination of the walls cause variations in plant colonization, especially in the case of travertine and less in the case of tuff, as a consequence of the differing porosity of these materials. The study also confirms the subordinate role of exposure with respect to other factors.