The Tarchonantho camphoratae-Oleetum cuspidatae ass. nov. - an Afromontane evergreen sclerophyllous community of the Arabian Peninsula with strong relationships to E Africa
Kürschner, Harald; Kilian, Norbert; Hein, Peter
The Tarchonantho camphoratae-Oleetum cuspidatae, an evergreen, sclerophyllous woodland community is described from W, SW and S Arabia as a new association. It is characterized by the Afromontane species Olea europaea subsp. cuspidata and Tarchonanthus camphoratus and can be classified in the here validated Pistacio-Eucleetalia schimperi of the Hyperico-Rhamnetea, both typical for E and NE Africa (Eritrea, Ethiopia, Sudan and Somalia). Owing to the wide distribution of the association and the different climatic conditions (influence of winter rainfall and summer monsoons in Arabia), three phytogeographical variants have been found, leaved rankless at present: a Rhus retinorrhoea-Barbeya oleoides variant of the Asir and Haraz Mts., a Rhus flexicaulis variant of Arays Mts., Jabal Gedu and Jabal Samhan, and a Rhus natalensis-Bauhinia ellenbeckii variant of the Kor Seiban. The species diversity in the understorey of the new association is extraordinary diverse (c. 240 taxa) and reflect these three variants by distinct chorological species groups. Whereas in the Asir and Haraz Mts. mainly Mediterranean, Irano-Turanian and Sahoro-Sindian taxa indicate the bi-seasonal Mediterranean type of climate, these ‘extra-tropical’ and ‘desert’ species are replaced in S Arabia (subtropical monsoon climate) by taxa of palaeotropical, Somalia-Masai and Afromontane origin (‘tropical’ species). They clearly reflect the strong floristic affinities of the S Arabian stands to NE Africa and the common floral history.