هاذا بحث عن الصحراء بشكل عاام
ما حصلت عن الصحراء في الامارات Sahara geographical region free or rare plant by "Sahara definition not Climatic plant," as lacking or scarce Alohat humans only in terms of available water, and little rainfall is less than 25 mm per year, and less life and the people who live on those circumstances Taklmwa harsh known in the Arab world Bedouin Examples deserts Empty Quarter desert and desert Aldhina in Saudi Arabia, the Sahara and also often be warm during the day and the desert cold at night and this is what is known Balaqarih in climate. Sahara word called tropical dry little rain, but desert areas are not necessarily empty and free of vegetation growth.
In most desert soils of many natural resources that always renewed. The desert soil and reduced by the existence of plant and animal life, but the types of animals and plants adapt with the desert climate, and adapt to live in it.
Scientists disagree on the definition of what is called Sahara, as some scientists wrote: "Every area of rain Aisagt where more than 25 cm per year, it is desert." One of the scientists is the type of soil and plant species mainly to identify the region and classification, and other scientists combine all these elements, Vitalegon name of the desert region a few plants, because of the lack of rain and dry soil.
Extends across most areas of desert areas with warm climate, but some areas near the north and south poles are considered other desert areas, note that the climate is cold freezing point, quick or no vegetation.
In this article, but would not touch land in the extended warm, covering about seven land area and most of this desert land in north Africa, and called the Sahara, an area of about 9000000 km ² are similar to land in Australia and the Arabian peninsula. See: Desert Aldhina; Empty Quarter desert; desert great influence. There are also Jobe Desert in China and Mongolia, and the Kalahari Desert in southern Africa. Deserts cover about 1.3 million km ² in the middle of North America.
The desert areas where urbanization difficult, but some people Taklmwa life under constant heat, drought lasting. In North America uses the population in the desert areas are Indians and Mexicans milk and mud to build their homes, preventing them scorching heat. , As does the population in the arid Arabian Peninsula.
Most of the population of the desert in Africa and Asia shepherds move from one place to another in search of water and pasture for livestock. The living tents and find their bodies in long clothes heat shield the hot sun and sand storms data.
In desert areas other people are using air conditioning in their homes, and rely on drilling wells for watering, making it easier to bear life in the desert environment.
Deserts. The seven total area of the land. Most desert lands extending the vicinity of the Tropic of Cancer north, south and the Tropic of Capricorn, and are subject to high pressure, where cold air drops, and when getting off heated and absorbs moisture rather than launching it in the air. Extends desert areas in other areas overshadowed elevations from the seas and oceans, as well as in the coastal areas.
Sand covers an area ranging between 10% and 20% of desert land. And the remaining land mostly Heights furnished demerits, rocks, etc., all of the soil to Atsaad the spread of plant life only within narrow, as they dry, but some of these rich soil salt, uranium and other minerals, in addition to underground resources such as oil and natural gas.
It also consists of desert lands of different types caused erosion and degradation, which has affected the soil and water draining mediated dry valleys and call Rill. And filled with rain water at the time of the crash on the mountain slopes and stooping and carrying water to the bottom of all the sediment and gravel rocks and sand, which is composed of masses of mud in the form of fan calls it alluvial fan. It consists also flat hills and plateaus flat surface called Mesa, also highlights the steep hills isolated called Botts, after rainfall carrying mountain water tables and salt to the salt lakes stomach, and gather where some evaporates, the rest part of the earth's surface, leaving salts accumulated in the bottom.
Saharitagti picture of the desert lands piles of sand, which posed wind, called've, these peaks rise to 250 m dunes, and always changing forms due to the impact of wind blew.
And along the desert oases composed, the most fertile regions, are beneath the eyes and tables, along with natural oases resident rights and industrial oases through irrigation and rainfall varies annual rate of $ 250 mm above the desert land from year to year. It stops raining for several years, and then come down heavily, in a few hours can not desert plants benefit from this abundant quantities of water at one go, taking Majkoveha of water, and the rest flowing on the Earth's surface, carrying with him the upper crust deposits to the soil.
Desert areas most regions of the world heat, as it absorbs the sun more than any other place, in the summer heat often rise daylight in the desert to 38 ° C and then declined during the night hours to 25 ° C, and winter temperatures moderated and the range between 10 ° and 21 ° C.
Life in the desert
Affected by desert plants here and there throughout the dry periods, and is seeking something from the little water available in the places he was, and then to pee only certain plants that took adequacy of water, and therefore are wide gaps between the plant and other plants wither and did not receive adequate water.
Some plants absorb water from groundwater, in America for example, there Mesquite trees, which absorb water at a depth of 12 m under the ground, trees and other store large quantities of water in their papers and roots and stems, such as the cactus plant to retain rain water Ventfaj leg, if it dried water shrink and shrink. There remains some plants flower after rains for a short period thanks to the water stored in their papers and stumps. Securities consume much water. If the ****ls available water trunk, and there are other trees have leaves very precise, it consumes only a little water available in the trunk, and keep the plant cut between seasons of rain. After the fall rains, the flowers bloom bright colors, thin trees and roots, and becomes a beautiful desert areas, and then lots of flowers that wither after the rain stopped.
Many species of plants and animals live in the desert regions. The picture shows some plants and animals that live in deserts. They have developed different ways of living to remain free despite severe weather and dry desert.
] Desert animals
Desert animals include a large number of insects, spiders and reptiles, birds and mammals. It also benefited to the desert, after the fall rains, wild animals such as deer, foxes and wolves, and others.
Most animals avoid extreme desert heat during the day, they come out only at night after low temperature. The insects and other small animals, staying in underground burrows all day, and are moving throughout the summer, and called animal static. The huge animals resort to places canopy all day Vnbard objects, as the water evaporates over the skin, and water offset another food that feeds them, and add water to the other if there are some depressions, as well as the digestion process adds water in the body of some animals such as camels, which benefit from this important water source, Jamal It could survive without water for several months. The sentences of another source of power in his body, as the Sanam Jamal repository of large quantities of fat, and he could live on this energy if dried body of water necessary.
] Sahara evolution and change
Provides irrigation water essential to the growth of crops in the desert. The irrigation project in the Libyan desert alfalfa farmers from cultivating their land. Most of desert land between two introduced 15 ° and 35 ° north and south of the equator, areas of high atmospheric pressure, with a cold wind blowing and then rewarmed. It consists of high pressure regions of the movement of wind on the earth, warm air emitted from the equator and come north and south. The higher the air temperature I said, and falling humidity drops him over the surrounding areas of the Equator. If the level of air service introduced 15 ° north or south, take Vischen landing again, and so composed droughts in the desert.
Tend to the drought situation also areas that separate heights on the seashore, because the winds blowing from the sea lose moisture, the higher summits over, Vnbard then decline towards the foot of the mountains inland, and lower temperature rose, and then dry. On this warm air dry up the rain is dry region, and scientists believe that the desert land in North America, consisting of similar land thousands of years ago, and since that time Algabr there has been no change in the natural factors constituting the desert.
However, the man had worked for the spread of these areas. Where the destruction caused millions of agricultural areas annually and all of the fertile belts adjacent to the desert lands as a result of lack of attention to service land, logging, overgrazing, and the opening of mines. Has taken some action to put an end to the destruction of fertile soil and desert encroachment and recover any damage to them, and between these procedures, tree planting in arid lands to reduce the impact of wind caused the encroachment of sand soil, and hence diversion winds from the crops, and a better techniques in the cultivation of the land, as well as reduce grazing on arid land. All these effective action to stop desert encroachment on agricultural land.