3rd lecture


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3rd lecture

  1. 1. Desert Ecology Dr.Abdulhadi Aloufi www.draloufi.com
  2. 2. Desert Soil:1. Hammada or Haswa Soil2. Regs or Desert Pavement3. Saline Soil4. Alluvial Soil5. Sandy Soil
  3. 3. 1. Hammada Soil: Hammade=Rocky DesertThis soil is characterized by : presence of high proportion of rocks. It is found in the flats, hills, uplands and the foothills of the mountains. The rocks of this type of soil returns to different geological origins such as granite, limestone, and basalt. This type of soil usually contains very low percentage of moisture, and grow on it few short scattered shrubs. The annual rainfall falling on such soils ranges between zero -200 mm.
  4. 4. ‫ﺻﺤﺮاء ﺗﻨﺰروﻓﺖ =ﻳﺳﻣﻴﻬﺎ اﻠﺒﺮﺑﺮ ﺑﻼد اﻠﺮﻋﺐ ﻠﺷﺪة اﻓﺘﻗﺎرﻫﺎ و ﻘﺳﻮة ﻤﺷﺎﻫﺪﻫﺎ‬ ‫اﻠﺼﺨﺮﻳﺔ اﻠﻣﻮﺣﺷﺔ اﻠﻣﻨﻔﺮة‬
  5. 5. 2. Regs or Desert Pavement: It is formed as a result of the movement of water and wind, which in turn convey the components of the soft soil of the high places to the nearby valleys. The sector of the soil is characterized by the presence of thin layer of red brown soil on surface, this thin layer usually contains a large proportion of the limestone compounds followed by gravel layer. The vegetation cover in this type of soil is simple where the amount of annual rainfall in these areas ranges between zero -200 mm.
  6. 6. 3. Saline Soil: It is found in desert areas and semi-desert semi-humid, especially near the shores of the sea and farms that have no scientific farming systems to get rid of accumulated salts. The percentage of salts in some soils reach to 10% of dissolved salts. The high percentage of salts in the soil is due to two reasons: 1. the rocky layer under the soil contains high proportion of salts. 2. The high water level to the upper layers of soil and evaporation, leaving behind it a quantity of salt deposited in the upper layers of the earths surface.
  7. 7. 4. Alluvial Soil It is found in the areas with high level of groundwater, it is normally found near the swamps and rivers and valleys with seasonal water. The layers are not well differentiated in the sector of this soil where the layers are homogeneous to a large extent and with soft soil able to retain large quantities of water. The alluvial soil with soft soil is found in less worm areas in the valleys, flats and over the highlands
  8. 8. 5. Sandy Soil Sand Desert= Erg = sand seas• Sand covers most areas of the Arab world.• The source of sand may be the same land that found on it or they have moved from another place by the winds, and currents of rivers or oceans.• The sand aggregates to form sand dunes which have several forms: A. Seif Dunes B. Transverse Dunes: C. Star Dunes: D. Barkhan Dune
  9. 9. A. Seif Dunes• This type is formed as a result of fast winds having one-way and bearing fine and coarse sands.• They appear as parallel lines moving with the wind.
  10. 10. B. Transverse Dunes:• This type is formed by winds of moderate speed, having one direction and bearing light sands. It is associated with the presence of wind and quantities of sands.• This type is found along the coasts and in the areas of the exposed sandy basement rocks for sculpture.
  11. 11. C. Star Dunes:• It is formed by winds blowing from different directions.• It is frequently found in the great desert and in the desert of the Empty Quarter.
  12. 12. D. Barkhan Dunes• It abounds in the regions with scarce sands and exposed to the winds of one-way.• It abounds in the dunes of the Arab and Asian deserts.• These dunes move at different speeds from one place to another.• It was known that it is capable for movement with a speed ranges from10-20 m per year
  13. 13. ‫ﺗﺘﻛﻮن ﻧﺘﻴﺟﺔ ﻠﻟﺮﻳﺎح اﻠﺳﺮﻳﻌﺔ ذات اﻻﺗﺟﺎﻩ اﻠﻮاﺣﺪ‬ ‫ﺗﺘﻛﻮن ﻓﻲ اﻠﻣﻨﺎﻃﻖ اﻠﻗﻟﻴﻟﺔ اﻠﺮﻤﺎل و اﻠﻣﻌﺮﺿﺔ ﻠﺮﻳﺎح‬‫اﻠﺤﺎﻤﻟﺔ ﻠﻟﺮﻳﺎح اﻠﻨﺎﻋﻣﺔ و اﻠﺨﺷﻨﺔ ،و ﺗﻈﻬﺮ اﻠﻛـﺜﺒﺎن‬ ‫‪Barakhan‬‬ ‫ذات اﺗﺟﺎﻩ واﺣﺪ .ﺗﺘﺤﺮك ﺑﺳﺮﻋﺎت ﻤﺨﺘﻟﻔﺔ ﻤﻦ‬ ‫ﺑﺷﻛﻞ ﺧﻄﻮط ﻤﺘﻮازﻳﺔ ﺗﺳﻴﺮ ﻓﻲ اﺗﺟﺎﻩ اﻠﺮﻳﺢ‬ ‫‪Dunes‬‬ ‫ﻤﻛﺎن ﺧﺮ ٠١-٠٢م/ﺴﻨﺔ‬ ‫ٓﻻ‬ ‫‪Seif‬‬ ‫‪Sand‬‬ ‫‪Star‬‬ ‫‪Dunes‬‬ ‫‪Dunes‬‬ ‫‪Dunes‬‬‫ﺗﺘﻛﻮن ﻧﺘﻴﺟﺔ ﻠﺮﻳﺎح ﻤﻌﺘﺪﻠﺔ اﻠﺳﺮﻋﺔ و ذات‬ ‫ﺗﺘﻛﻮن ﻧﺘﻴﺟﺔ ﻠﺮﻳﺎح ﺗﻬﺐ ﻤﻦ اﺗﺟﺎﻫﺎت‬ ‫اﺗﺟﺎﻩ واﺣﺪ و اﻠﺤﺎﻤﻟﺔ ﻠﻟﺮﻤﺎل اﻠﺨﻔﻴﻔﺔ .‬ ‫‪Transverse‬‬ ‫ﻤﺨﺘﻟﻔﺔ و ﻳﻛـﺜﺮ ﻫﺬا اﻠﻨﻮع ﻓﻲ اﻠﺼﺤﺮاء‬ ‫‪Dunes‬‬ ‫اﻠﻛﺒﺮى‬