Floristic traits of effusive substrata in North-Western Sardinia

The trachyte-basalt biogeographic sub-district of the north-western Sardinian district, included in the coastal and hill sub-sector of the Sardinian sector, is characterised by two large effusive complexes: Rhyolites, Andesites and Dikes of the Oligo-Miocenic limestone/alkaline cycle (14- 32 Myrs), and alkaline Basalts, Rhyolites, Rhyodacites and Dikes of the volcanic cycle with alkaline, transitional and sub-alkaline affinity of Pliocene-Pleistocene (0.14-5.3 Myrs). Between 2000 and 2002, 508 floristic/vegetation surveys were carried out on plant communities in order to improve the botanical knowledge and characterise this area biogeographycally. Floristic analysis, still in progress, led to detect 476 subgeneric taxa, as many as 23% of Sardinian flora. Among them, 44 endemics were found, as many as 20.5% of the Sardinian endemic flora. In the light of these results, the trachyte-basalt sub-region is characterised, with respect to the Sardinian flora, by significantly higher percentages of hemicryptophytes and lower percentages of therophytes; an increase in Eurimediterranean taxa is highlighted, whereas orophylous taxa are lower than the regional average; among the Mediterranean ones, the occurrence of a large number of western taxa stands out and is higher than the regional average, whereas eastern taxa are totally lacking.