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Atlas of Jordan

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Myriam Ababsa

Chapter one - Constraints and Resources

Biogeography

Carol Palmer

Texte intégral

1Jordan has a remarkably diverse flora with approximately 2,500 plant species. This diversity reflects the transitional position of the country between semi-arid and arid climatological zones. The overall climate, however, is broadly Mediterranean, characterized by the division of the year into a mild rainy winter and hot dry summer. Al-Eisawi (1985), following Long (1957), identifies nine bioclimatic regions, broadly grouped into four main clusters: Sub-humid Mediterranean, Semi-arid Mediterranean (warm and cool), Arid Mediterranean (cool, warm and very warm), and Saharan Mediterranean (cool, warm and very warm) (fig. I.18). Across all zones, it is the pronounced summer dryness, where drought coincides with the thermal maximum, which gives the vegetation one of its principal characteristics: its adaptation to aridity (fig. I.19).

2Four principal bioclimatic or biogeographical regions are recognized in Jordan: Mediterranean, Irano-Turanian, Saharo-Arabian and Sudanian (representing tropical penetration) (Kasapligil 1956; Jordan Country Study 2000a, 2000b; Long 1957; Al–Eisawi 1985, 1996). Limits between regions are indicative only, and some species can be found across several regions.

3Vegetation reflects many influences including geology, altitude, soil type and microclimate, with human activity also very important. A number of studies focus on the potential for agriculture, forestry and grazing, as well as taking into account the impact of human activity, in their classifications (Albert et al. 2003; Al-Jaloudy 2001; Kasapligil 1956; Long 1957; Ministry of Environment 2006).

Figure I.18 — Jordan’s Four Main Biogeographical Regions.

Figure I.18 — Jordan’s Four Main Biogeographical Regions.

Figure I.19 — Jordan’s Nine Main Bioclimatological Regions.

Figure I.19 — Jordan’s Nine Main Bioclimatological Regions.

Mediterranean bioclimatic region

4This region predominates in the highlands of Jordan, from Irbid in the north to Ras al-Naqb in the south. It is generally associated with altitudes above c. 700 m, but, in the north, where precipitation is higher, is found at lower altitudes. This zone has the highest precipitation, between 300 to 600 mm, and the lowest mean maximum temperature at 15-20°C, with minimum annual temperatures 5-10°C. The soil type is mainly Terra Rossa and yellow Mediterranean soil (Rendzina). It has the best land for rainfed arable agriculture and horticulture, and the highest tree cover. Ninety per cent of the contemporary human population live in this zone.

5Forest and maquis (shrubland) communities represent the most species-rich environments in Jordan. There are two main types of coniferous forest : wild Aleppo pine (Pinus halepensis Mill.) in the north, notably in the Dibbin forest, and wild Phoenician Juniper (Juniperus phoenicea L.) in the south, on sandy rock above 1,000 m asl. The strawberry tree (Arbutus andrachne L.) (plate I.2), and the rock-roses, C. villosus (syn. C. incanus L. subsp. creticus (L.) Heywood, C. creticus) and C. salviifolius L. often grow with the Aleppo pine, among others. Juniper forms pure stands but can be also found with Pistacia atlantica Desf. and Daphne linearifolia Hart, an endemic. Another conifer, Cypress (Cupressus sempervirens L.), notably grows in a small concentration in the Goethe Forest at ‘Ain Lahza.

6Broadleaf woodland communities are categorized by the domination of either evergreen or deciduous oak (plate I.4). Evergreen oak (Quercus calliprinos Webb. (syn. Q. coccifera L. var. calliprinos)) is the most widespread, growing both in the north and the south above 700 m asl, and covering c 25,000 hectares in total (plate I.1). Although classified as evergreen, many trees associated with evergreen oak woodland are deciduous, such as Pistacia palaestina Boiss., and hawthorn (Crategus azarolus L.). Deciduous oak woodland covers a smaller area, c. 4,000 hectares, and occurs at lower altitudes, between c. 100 and c. 750 m asl, forming open parkland. The taxonomic status of deciduous oak is not yet resolved. Al-Eisawi (1985) uses Q. ithaburensis Decne. as indicative, although other authors make further subdivisions. Species growing with deciduous oak vary considerably according to temperature and humidity. At Um Qays and Malka, it grows with Pistacia palaestina, carob (Ceratonia siliqua L.), Styrax officinalis L. and the common almond (Amygdalus communis L.), among others. At al-Alouk, it is associated with Pistacia atlantica, Amygdalus korschinskii (Hand.-Mazz.) Bornm. and Rhamnus palaestinus Boiss., among others. It can also be found with the wild olive (Olea europaea L.).

7Non-forested areas in the Mediterranean zone are described as ‘batha’ - Mediterranean dwarf shrub vegetation not exceeding 50 cm in height - and commonly identified as representative of degraded forest. Thorny burnet (Sarcopoterium spinosum (L.) Spach.) is widespread and typical. Common shrubs include Rhamnus palaestinus, white broom (Retama raetam Forssk. Webb.) and Calycotome villosa (Poir.) Link. In the south, white wormwood (Artemisia herba-alba Asso (syn. Artemisia sieberi Besser)), a characteristic steppe species, is frequently found penetrating into the Mediterranean zone, forming transitional batha-steppe.

Irano-Turanian Steppe

8The Irano-Turanian region surrounds the Mediterranean zone, forming a narrow strip of variable width, except in the north, where it extends eastwards along the Jordanian-Syrian border. Altitude typically ranges between 500-700 m asl. Precipitation is between 150 to 300 mm, and mean minimum annual temperature 2‑5°C and mean maximum annual temperature 15-25°C. Soils are mostly calcareous or transported by wind. This region is at the borders and below for rainfed agriculture, and predominantly used for grazing.

9Dwarf shrubs whose upper parts die back during the dry summer period, chaemophytes, are characteristic of this zone. Typical species include Artemisia herba-alba, which is considered more characteristic in the south, and Noaea mucronata (Forssk.) Asch. & Schweinf., in the north. Other common species include Retama raetam, Salvia dominica L., Ballota undulata (Sieber ex Fresen.) Benth., Anabasis syriaca Iljin, and many grasses, bulb plants and herbs. Artemisia herba-alba (plate I.5), Retama raetam, Astragalus spp., Trigonella spp., and grasses such as Stipa spp. and Festuca spp. are the most common pasture and forage species. Bulbs include sea squill, Urginea maritima L. (Baker) and Asphodelus aestivalis Brot., among others.

Saharo-Arabian bioclimatic region

10The Saharo-Arabian zone covers the mostly flat eastern semi-desert and desert, or Badiya, of Jordan, encompassing c. 80 % of the total land area. Mean altitude is c. 600-700 m asl, but rises to 1,200 m at the Jordanian-Syrian borders and drops to 520 m in the Azraq basin. Annual precipitation ranges between 100-150 mm on the border with the Irano-Turanian region quickly dropping to 50 mm further east and south. Mean annual minimum temperatures are 2-15°C and mean annual maximum temperature is 15-20°C. Soils are mostly poor and dominated by hammada, that is rocky plateau, including the basalt desert, but also includes saline and more sandy areas (plate I.10). Human population density is the lowest in Jordan, and this area is classified as rangeland for animal grazing.

11Vegetation cover is low and concentrated in the watersheds of wadis. Tree and shrub vegetation in the wadis varies and includes Retama raetam, Acacia spp., Tamarix spp. (well adapted to salty and sandy soils) and Phoenix dactylifera L. Wadi Butum, near Qasr Amra, is named for its concentration of Pistacia atlantica, a Mediterranean element penetrating into the Saharo-Arabian zone due to the presence of water there. Other perennial species found in this region include Achillea fragrantissima (Forssk.) Sch. Bip., Artemisia herba-alba, Astragalus spinosus (Forssk.) Muscl., Anabasis syriaca, and Anabasis articulata (Forssk.) Moq.. In mud-flat areas, such as Qa‘ al-Jafr, Qa‘ al-Disi, Qa‘al-Azraq and others distributed in the eastern desert, vegetation is exceedingly sparse due to water evaporation causing increased salinity and a hard crust to form that restricts plant life.

Sudanian bioclimatic region

12This region is considered to represent a penetration of tropical elements. Starting in the Jordan Valley to the north, it encompasses the area of the Dead Sea (plate I.12), the whole of the Wadi Araba to Aqaba and the granite mountains to the south, including part of Wadi Rum. Altitude falls to -400 m (below sea level), the lowest place on earth and a unique environment, rising as high as 1,200 m asl in the southern mountains. Precipitation is 50-100 mm, with mean annual minimum temperature 10-20°C and mean annual maximum temperature of 20-35°C. Soil is mostly alluvial, transported by water, saline, sandy and granite. The only inland sand dunes in Jordan are found here.

13Acacia woodlands and Ziziphus-Balanites formations are characteristic of much of the Dead Sea Depression and Wadi Araba. Acacias such as Acacia tortilis Forssk. Hayne and A. raddiana Savi Brenan are found throughout the area of the Dead Sea and Wadi Araba but particularly concentrate at the base of granite mountains. Ziziphus spina-christi (L.) Desf. may be found with Acacia, but Balanites aegyptiaca (L.) Delile only grows around the Dead Sea basin, along with species such as Maerua crassifolia Forssk. and Salvadora persica L.. Other notable species typical of the Sudanian region include Sodom’s Apple (Calotropis procera (Aiton) Aiton f.) and the Yisr tree (Moringa peregrina (Forssk.) Fiori). Sand dunes and sandy locations are characterized by the presence of Haloxylon persicum Bunge.

14Vegetation associated with water in the Sudanian region includes trees such as the date palm (Phoenix dactylifera L.), Black Poplar (Populus euphratica Oliv.), and willow (Salix acmophylla Boiss.). Saline (hydrophytic) vegetation grows immediately around the Dead Sea and lower Jordan River (fig. I.20).

Oak near Iraq al-Amir.

Oak near Iraq al-Amir.

M. Ababsa

Figure I.20 — Vegetation Types in Jordan.

Figure I.20 — Vegetation Types in Jordan.

Table des illustrations

Titre Figure I.18 — Jordan’s Four Main Biogeographical Regions.
URL http://books.openedition.org/ifpo/docannexe/image/4871/img-1.jpg
Fichier image/jpeg, 172k
Titre Figure I.19 — Jordan’s Nine Main Bioclimatological Regions.
URL http://books.openedition.org/ifpo/docannexe/image/4871/img-2.jpg
Fichier image/jpeg, 188k
URL http://books.openedition.org/ifpo/docannexe/image/4871/img-3.jpg
Fichier image/jpeg, 260k
URL http://books.openedition.org/ifpo/docannexe/image/4871/img-4.jpg
Fichier image/jpeg, 240k
URL http://books.openedition.org/ifpo/docannexe/image/4871/img-5.jpg
Fichier image/jpeg, 280k
Titre Oak near Iraq al-Amir.
Crédits M. Ababsa
URL http://books.openedition.org/ifpo/docannexe/image/4871/img-6.jpg
Fichier image/jpeg, 224k
Titre Figure I.20 — Vegetation Types in Jordan.
URL http://books.openedition.org/ifpo/docannexe/image/4871/img-7.jpg
Fichier image/jpeg, 152k

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