Vegetation [of the Arabian Peninsula]

The vegetation of the Arabian Peninsula is highly dependent on the arid climatic conditions, characterised by high temperatures and limited rainfall. The Arabian Peninsula is divided into several phytogeographic zones according to the distribution of plant communities conditioned by climatic conditions and their migration through time. Topographic, hydrographic and soil conditions, together with the impact of human activities, contribute to the composition of vegetation cover. Archaeobotanical research has revealed the exploitation strategies and evolution of past vegetation, as well as the emergence and development of agricultural biodiversity.

The Arabian Peninsula is divided into several phytogeographical units according to the regional distribution of plant communities (for detailed maps, see Ghazanfar & Fisher 1998: Fig. 4.2., p. 65). The Saharo-Arabian region (also called the Arabian regional subzone) covers most of the interior part of the peninsula and receives less than 100 mm of rainfall per year. It is characterised by very limited vegetation cover with a very low density of permanent species, mostly restricted to dune fields. Some of the main species composing this community are Astragalus tribuloides, Centaurea pseudo-sinaica, Cornulaca aucheri, Haloxylon salicornicum, Scrophularia deserti and Suaeda aegyptiaca (Ghazanfar & Fisher 1998: 66–67; Zohary 1973: 216).

A large part of the coastline surrounding the Arabian Peninsula (mostly in eastern and north-western Arabia) is included in the Nubo-Sindian Local Centre of Endemism, characterised by a tropical xerophilous tree vegetation cover. Temperatures are sufficiently high for tropical vegetation, but water resources are insufficient to maintain classical tropical plant cover. This vegetation is characterised by open thorn woodlands associated with discontinuous shrubby and grass cover, known in the scientific literature as a “pseudo-savannah”. This flora is composed of drought-tolerant species, including Acacia trees (Vachellia tortilis ssp. tortilis, V. tortilis ssp. raddiana), Calotropis procera, Capparis ssp., Chrozophora ssp., Cocculus pendulus, Halopeplis perfoliata, Pergularia tomentosa, Periploca aphylla, Salvadora persica, Tephrosia ssp., and jujube trees (Ziziphus spina-christi, Z. nummularia). The Oman peninsula, part of the Omani-Makranian or Omani-Sindian zone, includes several plant species considered to be relics of the Sudanian flora (Blepharis ciliraris and Ephedra pachyclada), which migrated from southern Arabia at the end of the Pliocene. This region also includes plant species in the al-Ḥajar mountains from Iran, Afghanistan and Pakistan (Convolvulus virgatus, Ochradenus aucheri, Physorrhynchus chamaerapistrum and Teucrium stocksianum), which migrated during the Pleistocene when the Persian Gulf was very low (Ghazanfar & Fisher 1998: 67–69, Zohary 1973: 240).

Southern and Southwest Arabia (broadly covering Yemen and southern Oman) are included in the Somalia-Masai regional Centre of Endemism (known also as the Eritreo-Arabian province of the Sudanian region). The vegetation of this zone is characterised by a xero-mesic tropical flora influenced by the summer and spring rains. Similarities with the eastern African flora can be observed with Senegalia asak, Berberis holstii, Boswellia sacra, Cadaba glandulosa, Carissa edulis, Commiphora spp., Diospyros mespiliformis, Dodonaea viscosa, Euphorbia spp., Ficus ingens, F. sycomorus, and Olea europaea ssp. africana. The plant communities of highland zones in the Yemen mountains, with high rainfall of more than 300 mm per year, are the Afro-Montane vegetation type, similar to those in mountainous areas of north-eastern and eastern Africa. This vegetation is constituted of dense forest formations dominated mostly by the evergreen tree Juniperus procera and composed of various trees, shrubs, and grasses, including Vachellia origena, Campanula edulis, Erica arborea, Helichrysum abyssinicum, Hypericum quartinianum, Jasminum abyssinicum, Rhamnus staddo, Rosa abyssinica and Salvia merjamie (Ghazanfar & Fisher 1998: 69–71, Zohary 1973: 244–247).

Vegetation distribution and composition in the Arabian Peninsula also depend on topographic, hydrographic and soil parameters, as well as the impact of human activities (Fig. 1). In mountainous areas, the composition and taxonomic richness of plant communities are determined by altitudinal ranges, but also by the cardinal orientation of slopes, which determines the degree of exposure to sun and evaporation (el-Keblawy et al. 2016). For example, in the higher altitudes of the al-Ḥajar Mountains, we observe open forest formations dominated by junipers (Juniperus excelsa ssp. polycarpos) and olive trees (Olea europaea), associated with shrubby (Clematis orientalis, Ephedra intermedia) and herbaceous (Teucrium mascatense, Cymbopogon nanthus) species. The presence of accessible water in areas situated in and near wadi beds leads to the development of hygrophilous taxa such as the Nile acacia (Vachellia nilotica), the teloukat fig tree (Ficus salicifolia ssp. cordata), and oleander (Nerium oleander), as well as the installation of date palm (Phoenix dactylifera) (Ghazanfar & Fisher 1998: 125–174). The sand dunes (e.g., Great Nefud, Jafurah, Roub al-Khali, Wahiba sands) are marked by the presence of psammophilous species which can withstand the mechanical instability of dunes and the lack of water and organic matter in the sediment with their adapted root systems and foliage, such as Artemisia monosperma, Calligonum comosum, Cornulaca monacantha, Cyperus conglomeratus, Haloxylon persicum and grasses (Panicum turgidum, Pennisetum divisum) (Ghazanfar & Fisher 1998, p. 191-208). The vegetation in coastline areas includes mostly halophilous taxa that can tolerate the high salinity content in the soil, such as Amaranthaceae (Arthrocnemum macrostachyum, Halocnemum strobilaceum, Halopeplis perfoliata, Salsola spp., Suaeda spp…), Zygophyllaceae (Zygophyllum spp.) and Plumbaginaceae (Limonium stocksii) species. Similar plant communities can be observed on the fringes of sebkhas (highly saline depressions due to evaporation during seasonal flooding) behind the lagoons and inland areas. Bays, lagoons, and wadi mouths also host monospecific mangrove formations (Avicennia marina being the most dominant species, Rhizophora mucronata, mostly in the Red Sea), adapted to the brackish environment and unstable soils by the development of particular root systems and the possibility to exudate salts through the leaves (Ghazanfar & Fisher 1998: 209–228). Several of these formations are now degraded due to human activities and notably over-grazing practices which prevent the regeneration of some plants and favour poisonous ones. More recent floral introductions have led to the dispersion of invasive species (e.g., Prosopis juliflora in Oman), disrupting local ecosystems (Ghazanfar 1998).

Archaeobotanical research has documented the long-term exploitation practices of past vegetation. Indeed, archaeobotanical discoveries of jujube stones (Ziziphus spp.) on the Neolithic site of Raʾs al-Ḥamrāʾ (Sultanate of Oman) have shown that wild fruits were gathered since Prehistoric times. Several fuel collecting practices from locally available plant formations have been observed since the Neolithic period, for example among littoral ecosystems in the mangrove (Avicennia marina, Rhizophoraceae), and in foothill areas, with taxa constituting pseudo-savannahs (Acacia spp., Prosopis sp., Ziziphus spp.) (for more details, see Bouchaud et al. 2016). Phytogeographical and genetic analyses have shown that the eastern part of the Arabian Peninsula may be one of the centres of date palm domestication (Phoenix dactylifera) (Gros-Balthazard & Flowers 2012). Since the Bronze Age (3rd–2nd mill. BCE), the region has seen the introduction of domesticates from peripheral regions (Near East, Iran), such as barley (Hordeum vulgare), wheats (Triticum spp.), lentil (Lens culinaris), pea (Pisum sativum), grapevine (Vitis vinifera), pomegranate tree (Punica granatum), leading notably to the installation and maintaining of oasis agrosystems in eastern Arabia (Tengberg 2012). Other cultivated plants have acclimatized locally over time during Antiquity and the first centuries of Islam, such as cotton (Gossypium spp.) in Northwest Arabia and sorghum (Sorghum bicolor ssp. bicolor) in Southeast Arabia (Bouchaud et al. 2018, Dabrowski et al. 2021).

Vladimir Dabrowski

See also:

• Barley (Hordeum vulgare L.)
• Cotton (Gossypium arboreum/herbaceum)
• Date palm (Phoenix dactylifera L.)
• Frankincense tree (Boswellia sacra)
• Myrrh tree (Commiphora myrrha)
• Sorghum (Sorghum bicolor (L.) Moench)
• Vine and Wine
• Wheat (Triticum sp.)

References and suggested reading

• Bouchaud, C., V. Dabrowski & M. Tengberg 2016. Etat de la recherche archéobotanique en péninsule Arabique. Routes de l’Orient Hors Série 2: 21–37.
• Bouchaud, C., A. Clapham, C. Newton, G. Tallet & U. Thanheiser 2018. Cottoning on to cotton (Gossypium spp.) in Arabia and Africa during Antiquity, in A.M. Mercuri, A.C. D’Andrea, R. Fornaciari & A. Höhn (eds) Plants and People in the African Past: 380–426. Cham: Springer.
• Dabrowski, V., C. Bouchaud, M. Tengberg, A. Zazzo & S. Priestman 2021. Archaeobotanical Analysis of Food and Fuel Procurement from Fulayj Fort (Oman, 5th-8th c. CE) including the Earliest Secure Evidence for Sorghum in Eastern Arabia. Journal of Arid Environments. DOI: 10.1016/j.jaridenv.2021.104512.
• Ghazanfar, S.A. 1998. Status of the flora and plant conservation in the Sultanate of Oman. Biological Conservation 85(3): 287–295.
• Ghazanfar, S.A & M. Fisher (eds) 1998. Vegetation of the Arabian Peninsula (Geobotany, 25). Dordrecht, London: Kluwer Academic.
• Gros-Balthazard, M. & J.M. Flowers 2021. A Brief History of the Origin of Domesticated Date Palms, in J.M. Al-Khayri, S.M. Jain, D.V. Johnson (eds) The Date Palm Genome. Vol. 1: Phylogeny, Biodiversity and Mapping: 55–74. Cham: Springer.
• El-Keblawy, A.A., A.H. Khedr & T.A. Khafaga 2016. Mountainous landscape vegetation and species composition at Wadi Helo: A protected area in Hajar Mountains, UAE. Arid Land Research and Management 30(4): 389–399. DOI: 10.1080/15324982.2015.1136970.
• Kürschner, H. 1986. Omanisch-makranische Disjunktionen. Ein Beitrag zur pflanzengeographischen Stellung und zu den florengenetischen Beziehungen Omans. Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 106: 541–562.
• Léonard, J. 1989. Contribution à l’étude de la flore et de la végétation des déserts d’Iran (Dasht-e Kavir, Dasht-e Lut, Jaz Kurian). Fasc. 9 – Considérations phytogéographiques sur les phytochories irano-touranienne, saharo-sindienne et de la Somalie-pays Masai. Jardin Botanique National de Belgique.
• Tengberg, M. 2012. Beginnings and early history of date palm garden cultivation in the Middle East. Journal of Arid Environments 86 (Nov. 2012): 139–147. DOI: 10.1016/j.jaridenv.2011.11.022.
• Zohary, M. 1973. Geobotanical foundations of the Middle East. Geobotanica selecta, Bd. 3. Stuttgart: G. Fischer.

_{Alternate spellings: Plants, Flora}