The trachybasalt biogeographic sub-district of the NW Sardinian district, included in the coastal and hilly sub-sector of the Sardinian biogeographic sector, is characterised by two large effusive complexes: that of the rhyolites, andesites and dikes of the Oligo-Miocene alkaline volcanic cycle (14-32 Ma) and alkaline basalts, rhyolites, rhyodacites and dikes of the volcanic cycle with alkaline, transitional and sub-alkaline affinity of the Pliocene-Pleistocene (0.14-5.3 Ma). Between 2000 and 2004, 156 surveys were carried out on shrub communities in order to improve knowledge of their phytosociology. Vegetation analysis led to the identification of 11 associations and 13 subassociations, referring to 3 syntaxonomic classes. Of these, 5 new associations are hereby described for the first time: Clematido vitalbae-Maletum pumilae, Crataego monogynae-Aceretum monspessulani, Lavatero olbiae-Rubetum ulmifolii, Genisto desoleanae-Ericetum arboreae and Telino monspessulanae-Cytisetum villosi
