Deserts and Semideserts

     Deserts and semideserts cover the vast areas of Central Asia, the Turan Lowland, the central part of the Plateau of Iran, the Penin­sula of Arabia and the lowland bordering on the Indus River. The greater part of the Asian deserts lie in the temperate zone; only the southern part of the Arabian Desert south of the Tropic of Cancer is in the torrid zone.

Fig. 92. An oasis with rich vegetation and cultivated land.
Owing to the dryness of the climate, plant and animal life is poorly represented. Desert plants do not crowd one another. They consist mainly of tough grass and scrubs growing at some distance from each other. These are not like the plants of well-watered lands. They have very small leaves that have ways of storing moisture. Some plants have thorns instead of leaves, other have no leaves at all. Local plants have long roots that either spread in all directions, sucking in moisture from the surface soil, or penetrate deep to the wetter layers, where they can take in the moisture necessary to their growth.
The'saxaul' (Haloxylon) is a tree peculiar to the deserts of Cen­tral Asia and the Turan Lowland. There occur growths of these trees called 'saxaul forests', though never so dense as real forests. The saxaul has either very small leaves or no leaves at all, and gives al­most no shade.

Fig. 93. Przhevalsky's horses. First discovered by Przhevalsky,   they roam the dry steppes and deserts of Central Asia

The wood of this tree is so heavy that it sinks in water, and so hard that the knife cannot cut it.
Sand desert vegetation is very poor. Yet there do occur plants, small and hardy, that help to strengthen the soil with their roots. If these sand-binding plants are destroyed by animals, then the sand is loosened and is easily blown away by the wind. Grains of sand are carried along until an obstacle is met to arrest their flight. Thus are barkhans (horseshoe-like sand-dunes) formed. The wind rolls the sand-grains from one slope of the barkhan to the other, thus causing the barkhan itself to shift before it. Fields, houses and sometimes entire villages are buried under the sand. To check this movement, plants are grown on the barkhans of Soviet Central Asia.
Vegetation is still poorer in clayey or rocky, pebble-strewn deserts. On the parched and clayey or rock-covered soil almost nothing can grow.
However, there are areas in the midst of the deserts which are made fertile by the presence of water.

Fig. 94. A stone desert on the Gobi Plateau.
(From a photograph by E. M. Murzayev, the explorer of Mongolia.) The granite hills are cracked and shattered by weathering. The spaces in between are covered with fragments of rocks. Two-hurnped camels are grazing on the sparse grass.

Along the banks of streams grow dense thickets of reeds, bushes and trees. In these areas called oases people make their dwellings, cultivating and irrigating the surrounding land.
On the watered lands of the deserts in the temperate zone grow poplar and fruit-trees, grapes and cotton. In the oases of the fiery Arabian Desert the date-palm is cultivated.
Though desert vegetation is poor, local plant-eating animals find sufficient food for nourishment. Various species of antelope and wild ass are found.
The wild camel and wild horse are natives of Asia and not to be found elsewhere. When in search of food or water, the wild horse is capable of covering vast distances. The camel is well adapted to desert life. It feeds on the tough, prickly plants and can do without water for days.

On the left and in the centre are antelope. In the background are yaks. One yak 1      is standing in the right foreground and behind him are some kulans (wild asses).
On hot summer days the desert seems lifeless. All living crea­tures avoid the broiling sun. They huddle in burrows or in the shade of shrubs by day and come out to feed at night. Some sleep through­out the summer months.
There are vast sand deserts in the Turan Lowland (the Kara Kum and Kyzyl Kum) and east of the Pamirs, between the Kunlun and Tien Shan mountain ranges.
On the Gobi Plateau semideserts and clay or stone deserts pre­dominate. Large areas are covered with fragments of weathered rock. Areas empty of plant life (barrens) stretch for dozens of kilo­metres.
The Plateau of Iran consists mainly of semideserts.
The desert is thinly populated. The inhabitants are engaged in sheep and camel-breeding. Only in the oases is there a thick agricul­tural population. In the desert regions of the Soviet Union big canals are being built. On the watered lands orchards are planted and cotton, rice and other important crops cultivated.
The Tibetan Plateau stands out for the peculiarities of its fea­tures. The rigorous climate and the stony and salty soil are unfa­vourable for plant life.
In the northern part of Tibet grow only small patches of grass, a few centimetres high. There are no trees whatsoever. Only along the riversides do scrubs occur.
In South Tibet the climate is milder, the vegetation richer. This part of the country is a dry steppe area. The ground cover consists

of grass that serves as food for the numerous grass-eating animals. In the valleys of East Tibet grow trees.
In the steppes of Tibet are found yaks— a kind of wild ox. These are large, strong and hardy animals with very long coarse, black hair that serves them as bedding when they lie down on the
cold  ground.
According to Przhevalsky, there are few places on earth with such a variety of animals. On the steppe pastures which are almost snow-less in winter graze great herds of yaks, wild asses called kulans and antelopes. There are myriads of rodents living in deep holes in the ground. On the mountain slopes graze mountain sheep.
The inhabitants of Tibet are engaged in cattle-breeding. There are plots of cultivated land here and there. At an altitude of 4,500 metres above sea level barley is sown. In no other place on earth is farming practised at such an altitude.
Questions and Assignments.

1. Mark on the outline map the desert zone of Asia.
2. What are the characteristics of the desert plants of Asia?
3. Why are rivers so important in deserts?