Floristic composition of volcanic landforms in Saudi Arabia is lacking. Therefore, the present study is carried out to assess the floristic composition, life form and chorology of the recorded species in Harrat ArRahah; ancient basaltic volcanic field lies south of Tabuk town. A total of 135 species belonging to 99 genera and 34 families were recorded. About 43% of the recorded species in the study area are belonging to five families of which, Asteraceae, Brassicaceae and Fabaceae have the highest contribution (38%). The data also reflects the high taxonomic diversity in the study area especially when compared with the ratio estimated for the total area of Saudi Arabia. Chorological characteristic of the recorded flora showed that Saharo-Arabian and Irano-Turanian elements constitute 48.1% of the total flora. Among the species recorded in the present study, fourteen species (10%) are endangered. Although Rheum palaestinum is mentioned in flora of Saudi Arabia as an extinct species, three individuals of this species is recorded in the study area. Astragalus collenettiae is the only endemic species recorded in the study area. The presence of Rheum palaestinum and Astragalus collenettiae in the ancient volcanic habitat of Harrat ArRahah, and because the area support a considerable number of the endangered plant species in Saudi Arabia, therefore, the protection of these landforms is of the utmost importance. Moreover, the area is botanically virgin and not explored extensively and intensively even though rich in vegetation, so, further detailed studies of the area are strongly recommended.
Key words: flora; endangered species; volcanic fields; Arabian Peninsula.
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