Northern Region

Topography and vegetation of Tabuk Region            

The regions in and around Tabuk are composed of metamorphic and igneous rocks. Western side of the region is bordered by a series of hilly and mountainous areas, particularly, the Jabal Lauz of Northern Hijaz Mountains, while the eastern and southeastern sides are bounded by the Great Nafud. Typical rangelands can be found on the Northern and southern sides of the Tabuk Province.  Altitude of the region varies from 750 to 1000m in most of the areas except in parts of the northern region where some of the plateaus and hilly tracts rise to an altitude up to 1500m. Topography is more or less similar to the Central Najd and consisting of wadis, hills and open plains. Most of the wadis are originating from the north western Hijaz Mountains and run in an eastward direction; of which some of them are part of the largest Wadi Rimah drainage. Wadis in general are filled with silty sand and gravel whereas the runnels close to the hilly areas that receive more local runoff is somewhat silty. However soil deposits in open plains vary from silts to sands to coarse boulders. Wadi Sirhan that cuts through the region is composed of a complex of alluvial soils varying from sandy to clayey, gravelly or in some areas it is saline. Some of the major agriculture centers can also be seen on the eastern and southeastern side of the Tabuk Town.

           In general terms, the vegetation of Tabuk Region is composed mainly of Chenopods, especially the Salsola tetrandra-Salsola cyclophylla associations. However, a few other xerophytic vegetations can also be seen in some localized centers. These localized vegetation units are dominated by Haloxylon salicornicum, Retama reaetam, Pulicaria undulata, Acacia tortilis, and Lycium shawii. On the western sides of the region, Acacia tortilis is dominating while on the southern sides Salsola spp. and Traganum nudatum are dominating. Along the northern borders where the soil is more sandy Haloxylon persicum and Artemisia monosperma form into communities, either singly or in associations with Stipagrostis, Cyperus, Cornulaca, etc. Tree species are rare in this region. However, species like, Acacia raddiana, Maerua crassifolia, Moringa peregrina, Ziziphus spina-christi, etc can be seen in some of the wadis.  Other perennials which form into communities in some parts of the region are: Salsola tetrandra, Traganum nudatum, Retama raetam, Artemisia sieberi, Hyoscyamus muticus, Astragalus spinosa, Haloxylon salicornicum, Rhanterium epapposum, Farsetia aegyptiaca,  etc. Apart from the xeromorphic vegetation, halophytic vegetation is also dominant in certain salt marsh ecosystems. These include: Pharagmites australis, Tamarix nilotica, Aeluropus lagopoides and Zygophyllum coccineum. A significant number of annual species are also found in the Tabuk region, most of which are belonging to the families, Brassicaceae, Asteraceae and Paplionaceae. Common annual species include: Eremobium lineare, Plantago boissieri, Anthemis melampodina, Cutandia memphitica, Silene villosa, Plantago ciliata, Savignya parviflora, Astragalus schimperi, A. annularis, Ifloga spicata, Trigonella stellata, Astragalus tribuloides, Schimpera arabica, Plantago amplexicaulis, etc.

Topography and Vegetation of Al-Jouf

Al-Jouf Region is about 550 m above sea level.  It is part of the extensive Al-Widyan Region that spreads in northwest to southeast direction. It is a complex of several wadis such as Wadi Ar’ar, Wadi Aba al-Qur, etc. that pass through limestone hills. Vegetation is composed of Salsola villosa and Atriplex leucoclada. The overall vegetation is highly degraded due to overgrazing and poor rainfall.  In Wadi Mayaala, about 20 km south of Ar’ar town, the frequency and density of several perennial species, particularly Heliotropium bacciferum and Aretemisia sieberi are very high. It is primarily due to the overall rainfall pattern experiencing in certain years. Yet, overgrazing combined with poor rainfall affect the overall vegetation structure of these areas. Rain in early winter has a significant effect in the vegetation of Ar’ar area rather than the rain in March-April period. In addition to the common plants, dwarf shrubs such as Achillea fragrantissima, Artemisia sieberi, Astragalus spinosa, Pituranthos triradiatus, Hammada salicornica and Artemisia monosperma can also be seen in many places. Although Salsola villosa and Atriplex leucoclada are common plant communities, at least few other associations like Salsola villosa-Traganum nudatum and Salsola tetrandra-Salsola cyclophylla associations can also be found on the edges of Ar’ar region. In certain places, occasional associations such as Rhanterium epapposum, Stipagrostis plumosa, Moltkiopsis ciliata, Polycarpaea repens, Convolvulus oxyphyllus ssp. oxyclada, Fagonia glutinosa, etc. are present. A significant number of annual species are also appearing during spring, the density of which depends on the rainfall. The most common species seen in this area is Spergularia diandra followed by Filago desertorum. Other common annual plants observed in this area are: Plantago boissieri, Eremobium lineare, Astragalus schimperi, A. annularis, A. tribuloides, Horwoodia dicksoniae, Cutandia memphitica, Plantago ciliata, P. ovata, P. amplexicaulis, Trigonella stellata, Lappula spinocarpos, Asteriscus graveolens, Artemisia scoparia, Herniaria hirsuta, Malva parviflora, Matricaria aurea, Tripleurospermum auriculatum. The density of annual cover varies from region to region. In some years, the density of Asteriscus graveolens is much higher than any other annual species or their presence is more or less similar to the plant cover of Spergularia diandra. Annual vegetation in the south of the region is also more or less similar to the north. Yet, in addition to the above annuals; species such as Paronychia arabica, Pteranthus dichotomus, Reseda alba, Gastrocotyle hispida, Aizoon hispanicum, Leotonodon laciniatum, Ifloga spicata, Helianthemum ledifolium, Picris cyanocarpa Schismus barbatus, Schimpera arabica, Roemeria hybrida, Calendula tripterocarpa and Medicago laciniata are also seen in shallow depressions and other silt areas