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Southern and Smaller Oases, the Western Desert

摘要: Description  Site # 1: Kharga OasisKharga Oasis occupies a depression in the southern part of the Western Desert of Egypt, extending for some 180 x 15-30 km in a north-south direction, at about 200 km

Description

  Site # 1: Kharga OasisKharga Oasis occupies a depression in the southern part of the Western Desert of Egypt, extending for some 180 x 15-30 km in a north-south direction, at about 200 km west of the Nile. The lowest point in the Oasis is more or less at sea level, while the highest is at 400 masl.The natural vegetation, as well as the naturalized species and the cultivated plants in Kharga and Dakhla Oases, seem to be more or less uniform, and to deal with each of them separately would involve an overlap which may approach a mere repetition. However, the peculiarities of each Oasis will be dealt with apart. Seven vegetation types are recognized in Kharga and Dakhla, described here mainly after Zahran and Willis (1992). The scientific names of plants throughout this listing are updated after Boulos (1995, 1999, 2000, and 2002).Site # 2: Dakhla OasisDakhla Oasis lies at about 120 km west of Kharga Oasis, extending for some 55 x 10-20 km in a northwest-southeast direction, at an altitude of 100-400 masl.1 - (a) Aquatic Vascular PlantsUrticularia gibba and Potamogeton pectinatus in freshwater (wells, reservoirs), Ruppia maritima and Zannichellia palustris, in brackish waters of shallow ponds, often associated with P. pectinatus, Najus graminea and N. minor, in shallow irrigation canals, Lemna gibba and L. aequinoctialis, free floating in most water bodies.1 – (b) Aquatic Green AlgaeNitella spp. and Chara spp., submerged green algae, often forming thick masses at the bottom of the water body and are attached to the mud by rhizoids, mainly in drains and stagnant waters.2 – Reed Swamp VegetationThis vegetation type is most pronounced around ditches, rice fields, wells, and in drains and pools. The most characteristic species of this type of vegetation are: Typha domingensis and Phragmites australis, usually associated with Cyperus rotundus, C. laevigatus and Pycreus mundtii. Other associates which may occur on the fringes include: Panicum repens, Desmostachya bipinnata, Conyza bonariensis, Alhagi graecorum, Ambrosia maritima and Prosopis farcta.3 – Halophytic VegetationTwo halophytic vegetation types may be recognized in the salt marshes:a.Wet salt marshes: Here the dominant species are Cyperus laevigatus, Juncus acutus, Suaeda aegyptiaca and S. monoica.b.Dry salt maeshes: The dominant species are Cressa cretica, Aeluropus lagopoides, Imperata cylindrica and Tamarix nilotica.4 – Psammophytic VegetationThis vegetation type occupies flat expanses of wind-drifted sand (the sand plains) and sand dunes, at different stages of development. The vegetation of the plains is usually richer in plant cover. The dominant species is Alhagi graecorum, associated with Stipagrostis scoparia, Calotropis procera, Aerva javanica, Tamarix nilotica, Hyoscyamus muticus, Suaeda vermiculata, Reaumuria hirtella, and Zygophyllum album. On the older stabilized sand dunes, Tamarix nilotica and Alhagi graecorum grow in anundance and may cover the summits and slopes of the dunes. In Baris town, at the southernmost tip of the Depression, Balanites aegyptiaca (heglig, or the desert dates), and Hyphaene thebaica (dom palm) trees are seen in thickets among the dunes.5 - Cultivated LandSeveral hundred deep artesian wells in Kharga and Dakhla provide the only source of water for irrigation. Some weels date back to the Pharaonic era, some to the Roman era, but most date from 1959 onwards, using modern technologies. Most wells are over-flowing, leading to the formation of salt marshes and abandoning the land to other areas. The date palm is the main cash crop of the two Oases, besides olive and other fruit trees. The date palm does not provide only dates, but also fibres, leaves, trunks, used locally or exported, for making basket, ropes, mats, sandals, furniture, building material, agricultural tools, and numerous other items. It is a culture based on and supported by the date palm. Some vegetables are also cultivated for local consumption. Rice (Oryza sativa) is cultivated on a small scale, besides some other cereals such as millet (Pennisetum violaceum) and sorghum or broom corn (Sorghum bicolor). Some other grasses are cultivated for fodder, such as Sudan grass (Sorghum x drummondi). No wheat and barley re cultivated due to soil salinity.6 – Waste LandIn the vicinity of cultivated ground, vast areas are usually abandoned and neglected. The major elements of this habitat type are: Zygophyllum coccineum, Tamarix nilotica, and Alhagi graecorum, which reflect the rather saline soil. Among the associated species are Hyoscyamus muticus, Sporobolus spicatus, Fagonia arabica, Cyperus laevigatus, Aeluropus lagopoides, and Polypogon monspeliensis.7 – Xerophytic VegetationThis type occupies the desert ecosystem, mainly around the Oases, and is particularly part of the Western Desert flora, with an extensive list of vascular desert plants, which is outside the scope of this brief description.Endemic SpeciesCompared to other areas in Egyptian deserts, there may be few endemic species restricted to Kharga and Dakhla Oases. They are: Ducrosia ismailis Asch. and Pimpinella schweinfurthii Asch., both in the Family Umbelliferae, in Kharga. Melilotus serratifolius Täckholm & Boulos (Leguminosae), is endemic to Dakhla Oasis.Rare SpeciesRhazya stricta Decne. (Apocynaceae), is known in Egypt only from Kharga Oasis. Its occurrence in Kharga represents the westernmost locality in its geographical range of distribution, which extends eastwards to Arabia, Iraq, Iran, Afghanistan, Pakistan, and India, and southwards into Sudan. The above three endemic species, as well as the rare Rhazya, are known only from one or very few collections, and are therefore to be classified as threatened species.Rare AnimalsThe endemic oligochaete Nannodrilus staudei, discovered in the Nile region and described by Michaelsen in 1887, was discovered in 1969 by S. Ghabbour from Ain Khosh, in the south of the Kharga Oasis.Site # 3: Kurkur and Dungul OasesKurkur and Dungul Oasies are small uninhabited oases within spectacular escarpments from the Nubian Tableland to the Lower Nubian Plain in the southern part of the Western Desert. They lie at the edge of the Sinn El-Kaddab Plateau. The distance between the two relict Oases is about 60 km. Kurkur Oasis is considerably larger than Dungul, which consists of two parts: Dungul Oasis proper and Dineigil Oasis. Dineigil is located at the very edge of the escarpment in a high position while Dungul is in a lower position in the Wadi Dungul. Both Oases receive their water as a result of the blockage of drainage lines of an artesian aquifer. The two Oases and the area ibetween comprise a great variety of landscape features and habitat diversity. Of special importance is the fascinating white limestone erosion-bounded Dineigil and Dungul Oases. In spite of almost rainlessness, these two Oases are rich in biodiversity. Palm groves (three species) and extensive growth of Acacia groves form the main framework of the perennial plant cover. The highlight of the floristic characteristics is the occurrence of the long forgotten palm Medemia argun, which was abundant in Ancient Egyptian times but is now found only in Dungul and in another spot in northern Sudan. It can thus be considered in modern times to be endemic for the Nubian Desert, and also threatened with extinctio, although some young individuls are still growing there. The fauna of this area needs further studies. There is some evidence that these Oase are the very last refuges of viable populations of the highly threatened dorcas gazelle Gazella dorcas, and maybe also the highly vulnerable and extremely rare Sand Cat Felis margarita, in the Western Desert of Egypt. The two Oases also contain many important Neolithic sites which are so far well preserved.Site # 4: Moghra OasisMoghra Oasis is a small uninhabited oasis, situated on the north-eastern edge of the Qattara Depression, bordered by by a brackish-water lake, constituting the lowermost part of the Oasis (-38 m), occupying an area of about 4 sq. km. Salt marshes border the lake in some of its parts. Sand formations are dominant in the western and southern edges of the lake, either in the form of dunes close to the lake, or as deep sand sheets away from it. The plant cover is a combination of reed swamps, salt marshes, and dsand formation vegetation. The saline flats are dominated by Juncus rigidus between the lake and the sand formations, associated with Phragmites australis, Tamarix nilotica, Limbarda crithmoides, Nitraria retusa, Cressa cretica, and Arthrocnemum macrostachyum. The sand formations are dominated by Zygophyllum album, Nitraria retusa, Tamarix nilotica, Alhagi graecorum, and Sporobolus spicatus. These are associated with Artemisia monosperma and some neglected date palms appearing in groves of variable sizes.Site # 5: Wadi El-Natroun DepressionWadi El-Natroun Depression is a narrow depression located in El-Beheira Governorate, in the Western Desert, west of the Nile Delta, approximately 110 km northwest of Cairo and 90 km south of Alexandria, in a NW-SE direction. It is an oasis rather than a “wadi”. The name wadi was gained for its longitudinal shape. It is about 23 m below sea level. It is fed by water reaching it by seepage from the Nile Delta. The inflow covers large parts of the slopes on the NE side of the lakes, giving rise to distinctive marshes on water-logged soil, encrusted with salt due to the high evaporation rate. In contrast to this landscape, the opposite shore on the SW side is almost devoid of a transition zone where it meets the desert. Except for Lake Al-Gaar, the lakes are known for their hypersaline water, due to the presence of high salt concentrations. This salt-laden underground water contains different salts due to its infiltration through different salt-containing strata.Tectonic forces played an important role in the formation of the Wadi El-Natroun Depression. Several fissures and faults resulted from these forces as easy passages for underground water which carries soluble components of the rocks underneath, leaving residual deposits on the surface, mainly of sodium carbonate (natron, hence the name Natroun). This natron was at the basis of the soap industry in Europe till the middle of the 19th century, when the method used by the Frenchman LeBlanc, who discovered how to produce it synthetically, became widespread. About 20 lakes are found in the central part of the Depression. These lakes differ in size as well as in seasonal permanence. They are disconnected by a wind blown sand barrier, but are believed to have been one continuous lake in the past. The small lakes dry up completely in summer due to evaporation. In winter, they are overflooded with water when inflow exceeds evaporation. The larger lakes, on the other hand, contain permanent water all year round, reaching a maximum extent in winter, but are much diminished in summer. The known permanent lakes in the Wadi El-Natroun Depression are about 10 in number. The origin of the underground water in Wadi El-Natroun is seepage from the Nile stream, due to its proximity and low level. Before the construction of the Aswan High Dam, the water level in the lakes of Wadi El-Natroun closely followed the water level rhythm of the Nile flood, with a time lag of 2-3 months. After that, it now follows the rhythm of the regulated water level of the Nile, as water is periodically released from Lake Nasser in the south of Egypt, for purposes of irrigation or for hydro-power.Some of the principal lakes are:·Lake Fasida: An oval-shaped lake about 8 km from the southern end of the Depression, with an area of about 1.5 sq. km, 21 m below sea level in its northern end. It completely dries up in summer The bottom of this Lake is reddish, and the amount of natron it contains is very low, but it is surrounded by crusts of that salt.·Lake Umm Risha: Of an area of about 2.9 sq. km, and 21.9 m below sea level. About two-thirds of it is dry in summer and there are thick deposits on its bottom. The amount of natron is limited and its water is reddish.·Lake Al-Gaar: Area 1.9 sq. km, in the extreme north of the Depression and it doesn’t dry up.·Lake El-Zugm: Area 1.9 sq. km, in the center of the Depression, dries up in summer and has deep natron deposits.There are two main ecosystems in Wadi Natroun: (1) Salt Marsh Depressions and (2) the Gravel Desert. These comprise: (a) reed swamp vegetation and (b) salt marsh vegetation, which is in turn divided into dry salt marsh vegetation and wet salt marsh vegetation, and (c) halfa vegetation. This differentiation is due to soil salinity and level of ground water. Depending on the relief, the following habitat conditions are recognized:·Localities with the lowest relief have a continuous underground water supply, and predominating swamp conditions. These localities represent the typical reed habitat.·Where the water table is shallow, the soil is darkish brown and very rich in organic matter. High evaporation and lack of rainfall lead to increased salinity. Under such conditions the wet salt marsh habitat is formed. Where the sandy soil is relatively dry but still saline and organic matter content is low, the habitat of dry salt marsh is formed.·Halfa (Imperata cylindrica)grassland, the types of vegetation in this habitat are sand terraces or sand dunes.·The gravel desert habitat, surrounding the Wadi Natroun Depression, is a part of the gravelly Western Desert landscape dissected by drainage runnels varying in size. Plants in this sand-gravel desert depend mainly on the amount of the scanty rainfall. A noticeable feature of this habitat is the mosaic pattern of the vegetation, suggesting that the plants are affected by several interacting factors, other than rainfall alone.Only 46 plant species were recorded in the Depression. Of these, 42 are perennials and only 4 annuals. They represent about 2.3% of the total flora of Egypt. The most striking observation is that the highest richness is reached in the dry salt marshes and the gravel desert, both habitats being characterized by strong heterogeneity of microsites. There are direct and indirect causes for species impoverishment in the Depression, related mainly to the ways in which Man has used natural resources through time. Continued uncontrolled wood-cutting, overgrazing, establishment of fish farms, rainfed farming for annual crops, and land reclamation for irrigated agriculture, have dominated the Depression for many centuries, but have become very intense in the last decades. The net result has been the reduction of vegetation cover and the impoverishment of the flora. . The papyrus of the Ancient Egyptians, Cyperus papyrus, was rediscovered in 1968 there, and the Wadi Natroun is still the only place in Egypt where papyrus exists in a natural state. Individuals of this small population were tried to revive the papyrus paper industry in Egypt about 40 years ago, but they proved inadequate, and other taller individuals were brought from Lake Chad and southern Sudan and replanted on the Nile banks in Cairo. These new plantations are the basis of the now flourishing papyrus paper trade in Egypt.As to animals, 173 vertebrates (mammals, birds, reptiles, and amphibians) have been recorded. Birds alone are 117 species. Most of them are passerine or winter visiting water birds, since the Depression is a link in the chain of water spots along their migration routes. Cyperus laevigatus dominates the wet salt marshes on the eastern shores of the lakes, creating one of the most characteristic and attractive habitats for water birds. It is important for Common Cranes. The most common birds are Shelduck, Great Snipe, Curlew, Little Stint, and Kittlitz’s Plover, which may reach 1200 individuals in winter time. Such significant bird populations in Wadi Natroun are of considerable economic importance as they represent an attraction for eco-tourism. Birds play also an important role in food chains in this area.The bird fauna in Wadi Natroun is under stress due to hunting parties sport and trapping for trade, although most of these birds are under legal protection. The Marbled Teal, was a breeding bird in Wadi Natroun untill 1912. Last observations of this species show that it is unlikely that it will breed again here. There are two bird species here that are included in the 1996 IUCN Red List of Threatened Animals, the Marbled Teal and the Great Snipe. The Graceful Warbler, Wadi Natroun form, is endemic here. Wadi El-Natroun has been designated one of Egypt’s 34 Important Bird AreasMammal species are 31, reptiles 24, and only one amphibian. Hunting parties are common in the inland desert, for hares and foxes. Five of these mammals are listed on the 1996 IUCN Red List of Threatened Animals, one of which being the endemic Flower’s shrew, Crocidura floweri.Efforts should be directed to protect the habitats of reptiles, particularly the Grass Loving Lizard, Philochorus intermedius, endemic and recorded only from Wadi Natroun.Wadi Natroun is notorious for being the endemic spot in which the liver fluke, Fasciola, which attacks sheep and occasionally humans, exists. The Wadi Natroun is a focus of endemism of this fluke, from where it spreads to the Delta when flocks of sheep are brought sometimes here for grazing.Since the time of St. Antonios of Egypt, and for the last 17 centuries, the Wadi Natroun was a haven for monasticism. It was called in ancient Coptic texts the Wilderness of Shit (the soul). Several Monasteries were built and rebuilt over that time, but now only four exist. The monks spent their time in basket weaving, using the reeds, and salt extraction. Now they reclaim land surrounding the Monasteries and use high technology for farming, and for publication of theology books and manuscripts. The Monasteries are rich in works of religious art and in ancient manuscripts.


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