Omanian Upland Acacia-Commiphora Woodland
In the Dhofor Mountains these include Acacia tortilis and various Commiphora species such as C. foliaceae, C. gileadensis and C. habessinica. Other woody associates include several endemic or near endemic species like Acridocarpus orientalis (Malpighaceae), Anogeissus dhofarica (Combretaceae), Boscia arabica (Capparaceae), Ceratonia oreothauma subsp. oreothauma (Fabaceae), Maytenus dhofarensis (Celastraceae), Jatropha dhofarica (Euphorbiaceae) and Prunus arabica (Rosaceae).
Omanian Juniperus excelsa subsp. polycarpus Woodland
This juniper is found from Turkey to India but on the Arabian Peninsula it is confined to isolated population on Jebel Akhdar in the northern mountains of Oman. At high altitudes above about 2400 m it is the dominant species forming open woodlands, but at lower levels it is often co-dominant with Olea europaea. The two most common associates are the perennial Cymbopogon schoenanthus and the near endemic Euryops arabicus (Asteraceae). The few other associates include Daphne mucronata, Monotheca buxifolia and the near endemic Lonicera aucheri (Caprifoliaceae).
Omanian Dichanthium Savannah
Over much of the Salahah plain the vegetation is dominated by the endemic or near endemic grass Dichanthium micranthum (Poaceae). On the more level areas it can form almost pure stands. Other grasses may include the graceful Stipagrostis paradisea with its attractive feathery plumes. However, many wadis draining from the Qara Hills dissect the plain and these provide added ecological diversity to the area (see below).
Omanian Southern Escarpment and Plateau Vegetation
On the south facing, limestone slopes of Dhofar, which receive monsoon mist and clouds, deciduous woodlands occur mainly characterized by the endemic Anogeissus dhofarica (Combretaceae). Other common or co-dominant trees include Commiphora abyssinica var. simplicifolia and Delonix elata. The associated shrubs include Allophylus rubifolius, Premna resinosa, Trema orientalis and the endemic or near endemic Blepharispermum hirtum (Asteraceae), Croton confertus (Euphorbiaceae) and Maytenus dhofarensis (Celastraceae). The former is a curious plant with florets disposed in dense spherical heads. Also found here are several suffrutices including the two endemic or near endemic species Barleria aucherana (Acanthaceae) and Hybanthus durus (Violaceae). Smaller ground layer species include Meineckia phyllanthoides, Polygala rotundifolius, Desmodium ospriostreblum, Physalis micrantha, Justicia heterocarpa and the endemic or near endemic twiner Ceropegia boerhaviifolia (Asclepiadaceae). On the lower slopes the Arabian endemic Boscia arabica (Capparaceae) becomes the more prominent species often festooned with the widespread succulent vine Cissus quadrangularis. Other woody associates include the endemic Jatropha dhofarica (Euphorbiaceae), and of special interest in these woodlands in the presence of species of the endemic genera Cibirhiza (Cibirhiza dhofarensis) and Dhofarica. The ground cover consists of a thick layer of herbaceous shrubs, climbers and ferns. At altitudes exceeding about 500 m these deciduous woodlands gradually give way to semi-evergreen thickets dominated by Carrisa edulis, Dodonaea angustifolia, Euclea schimperi, Euphorbia balsamifera and Olea europaea. Moving even higher, on to the summits, grasslands with Apluda mutica and species of Cenchrus and Themeda replace the thickets. Among the associated herbs are Impatiens balsamifera and the endemic Dyschoriste dalyi (Acanthaceae). Further inland where the influence of monsoon mists decline xerophytic trees, shrubs and succulent herbs predominate. These include Acacia ethaica, Dracaena serrulata and the endemic Cocculus balfourii (Menispermaceae) and Dhofarica macleishii (family?).
Omanian Wadi Vegetation
The vegetation of wadis can vary from place to place. On Salahah plain they include shrubs such as the endemic Commiphora foliacea (Burseraceae) and Zizyphus leucodermis (Rhamnaceae). The sandy gravel in the middle of wadis may include Anticharis glandulosa, Commicarpus boissieri, Gossypium herbaceum, Heliotropium dasycarpum, Fagonia socatrana var. somalica, Tricholaena teneriffae, and the endemic or near endemic Lavendula subnuda (Lamiaceae), together with the near endemic grass Eragrostis mahrana (Poaceae). The latter was originally described from the Hadhramaut and named after the Mahra tribe whose territory lies in south Yemen immediately to the west of Dhofar. The banks of wadis may also have a distinctive assemblage of species. For example, in some of the western wadis, the north facing banks include Barleria acanthoides, Boerhavia elegans, Endostemon tenuiflorus, Tribulus terrestris, Saddera latifolia and the near endemic Pavonias subaphylla (Malvaceae). Wadi Ayun represents, a northward-draining wadi, is a deep gorge that has been carved through limestone. In the dryer parts of this and its tributaries the gravel beds include species such as Tamarix mannifera and several endemic or near endemic species such as Anticharis arabica (Scrophulariaceae), Euphorbia arabica (Euphorbiaceae), Lavendula nimmoi (Lamiaceae), Trichodesma boisseri (Boraginaceae) and the strange parasitic species Cistanche rosea (Orobanchaceae). Wadis in this part of the world are also known for their celebrated frankincense (Boswellia sacra), which can be found, for example, in abundance in Wadi Adawnib. Its vivid dark green leaves making it a conspicuous part of the landscape. Other endemic or near endemic species associated with the wadis of this BioProvince include Barleria aucherana (Acanthaceae), Polygala dhofarica (Polygalaceae), Reseda sphenocleoides (Resedaceae), Teucrium yemense (Lamiaceae) and Trichodesma cardiosepalum (Boraginaceae).
Omanian Gravel Plain Vegetation
Gravel plains are found throughout central and eastern areas and although these are classed as hyper arid, frequent fogs and dew formation supplements the available water. The vegetation largely comprises open Acacia scrub with A. ebrenbergiana and A. tortilis, together with Prosopis cineraria and the endemic Ziziphus leucodermis (Rhamnaceae). Shrubs of more limited distribution are Pulicaria glutinosa and the near endemic Rhazya stricta (Apocynaceae). The ground layer includes several grasses such as Stipagrostis sokotrana, which is an important food source for Arabian Onyx, while other notable species include Nannorrhops ritcheana, Pulicaria undulata and the endemic Convolvulus oppositifolia (Convolvulaceae) and Pulicaria pulvinata (Asteraceae). Of interest in coastal limestone areas is the endemic Hyoscyamus gallagheri (Solanaceae).
Omanian Semi-Desert Grassland
These grasslands once dominated the southern coastal plains, but much has now been lost to human intervention and over grazing. Nevertheless, after rain grasses and ephemeral herbs still appear over relatively large areas. Scattered trees of Acacia tortilis are also present together with various xerophytic shrubs such as Caesalpinia erianthera and species of Cadaba and Commiphora. Associated species include Adenium obesum, Euphorbia cactus, Kleinia odora, Sansevieria ebrenbergii and the endemic Caralluma flava (Apocynaceae). At the foot of mountain slopes there is a distinctive zone dominated by the endemic Boscia arabica (Capparidaceae). This zone is also important for the generic endemic Cibirhiza dhofarensis (Apocynaceae) together with the endemic or near endemic Croton confertus (Euphorbiaceae) and Jatropha dhofarica (Euphorbiaceae).
Omanian Xeromorphic Open Scrub
Dry, open scrub largely dominated by Commiphora myrrha and Euphorbia larica occur on karstic coastal terraces. Other common species are Acacia ethbaica, Grewia tenax var. erthraea and Ochradenus arabicus, all of which are characteristic of this rugged karstic relief with rapid water run-off and pronounced erosion. However, species composition varies. On the mountain range south of Madinat Qabus, which is mainly karstic limestone and dolomites, the dominant taxa are jointed by various endemic or near endemic species. These include shrubs such as Ochradenus aucheri (Resedaceae) and Rhus aucheri (Anacardiaceae), chamaephytes such as Jaubertia aucheri (Rubiaceae) and Teucrium stocksianum (Lamiaceae), hemicrytophytes such as Caralluma aucheriana (Apocynaceae), Convolvulus virgatus (Convolvulaceae) and Diplotaxis harra (Brassicaceae), and therophytes like Herniaria mascatensis (Caryophyllaceae).
Omanian Halophytic Vegetation
This includes vegetation of saline plains, saltpans and sabkhas, but not coastal saltmarsh. However, a number of inland halophytic assemblages overlap with the less saline coastal habitats forming mosaics of in which both inland and coastal halophytes occur. Inland stands are often dominated by Suaeda fruticosa, whereas on the Barr al Hikman Peninsula the large sabkha is dominated by Atriplex farinosa and the endemic Suaeda moschata (Chenopodiaceae), but these are replaced by monospecific stands of Arthrocnemum macrostachys where loamy soils predominated. Saltpans, on the other hand, are typically fringed with Halopeplis.
Further information required.
References
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Fisher, M., Ghazanfar, S. A. & Spalton, A. 1999. The Natural History of Oman. Backhuys Publishers, Leiden.
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