Influence of environmental factors on the chamaephytic vegetation of pebbly alluvium of southern Tuscan river beds (central Italy)

The results of an ecological and phytosociological study of the chamaephytic vegetation on the first two alluvial terraces of several river beds in southern Tuscany (central Italy) are reported. A strong correlation between the various plant communities and the degree of disturbance by flooding and with pedogenesis was observed. A new subassociation of Santolino etruscae-Saturejetum montanae, growing on terraces with incoherent substrate frequently disturbed by flooding, is described. Some fundamental factors, namely the ecological and structural features of the individual vegetation stands, clarify the autonomy and syntaxonomical collocation of the coenoses studied.