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West Saharan Montane Xeric WoodlandsThe West Saharan montane xeric woodlands is an ecoregion covering part of the Sahara. The Sahara is the world's largest desert and is located in northern Africa. It streches from the Red Sea to the highlands of Ethiopia. However, the Sahara encompasses regions significantly different from an ecological perspective. The surface of the desert ranges from large areas of sand dunes (which are called erg), to stone plateaus (hamadas), gravel plains (reg), dry valleys (wadis), and salt flats. The northern and southern margins also receive more rainfall and have greater vegetation than central Sahara. The very scarse rain (less than 25 mm and even less than 5 mm per annum in the east) can fall in any season and in a very irregular way : some areas may receive no rain for years then suffer intense storms. Some areas encompass vast underground aquifers resulting in oases, while other regions severaly lack water reserves. Some mountains (Ahaggar, Tassili NAjier, Tibesti, Ar) also rise up in the desert and receive more rainfall and mostly present slightly cooler summer temperatures. For such reasons, the great Sahara may be divided in several ecoregions and each of them be separately described. Overview The boundaries for the largest part of this ecoregion, which includes the Tassili-n-Ajjer Ahaggar and Ar ou Azbine massifs, follow the regs, hamadas and wadis above the 1000 m contour. This covers a good part of southeast Algeria. These areas are reaching almost 3000 meters Additional areas further south were included within this ecoregion, including the Ar ou Azbine in northern Niger, Dhar Adrar in Mauritania, and Adrar des Iforas in Mali and Algeria, using the 500 m-elevation contour. This ecoregion has an area of 258,100 km2 (99,700 square miles) The mountains of the West Saharan Montane Xeric Woodland ecoregion are found within the Sahara Desert and are predominantly of volcanic origin. They rise from the surrounding flat desert landscape or sand dunes and create islands of moister habitat (guelta) which support flora and fauna. The most important area is the Tassili-n-Ajjer Plateau, an outlier of the Ahaggar Mountains in Algeria which supports some near-endemic species and some globally threatened antelopes. The highest point of these mountains is 2918 meters (Tahat). Winters are quite rigorous, with amplitude in temperature over 20C. Day temperatures may be over 20C while nights are freezing. In summer, days are very hot, though less than in central Sahara. Rainfall is rare and sporadic. The human population of the ecoregion is very small, with less than 5 persons per km2. Many people are nomadic though some small cities also exist (ideles). The vegetation remains fairly intact.
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