DESERT ECOSYSTEM

1. DESERT ECOSYSTEM

2. Types of deserts • Tropical deserts – southern Sahara in Africa • Temperate deserts – Mojave in Southern California • Cold deserts – Gobi in China

4. Deserts cover about one-fifth of the Earth’s land surface. • Most deserts are near the Tropic of Capricorn or the Tropic of Cancer. • Deserts can be found all around the world, particularly in southwest United States, south America, northern Africa, central Australia, the middle east, and China.

5. Deserts: where & why Deserts & winds

8. Desert – an ecosystem found where there is very little rainfall. • Deserts are dry and hot. There are very few clouds. • Two kinds of deserts: • Hot deserts • Cold deserts • Hot deserts • Temperatures are very warm all year round • The summers are very hot • Cold deserts • Short, warm summers • Long, cold winters • Found in places near the north and south poles

9. Location • The Sahara desert covers the northern section of Africa, and spreads over almost all the “top of the continent, it is the largest hot desert in the world, as well as the second largest desert on earth after Antarctica.

10. Climate • Deserts are areas of land that usually receive less than thirty centimeters of rain each year. • Deserts have cold nights, and extremely hot days. • Most deserts usually receive about fifteen centimeters of rain each year.

11. Climate (Atmosphere and Hydrosphere) • The desert temperature is not always hot. During the night, desert temperatures are quite cold, even below freezing point. The daytime temperatures are hot because there is very little cloud cover. This means that maximum radiation from the sun reaches the surface of the earth. In summer the temperature can reach as high as 40°C, while in winter, the temperature can reach 24°C.

12. Large diurnal range • At night time, the lack of cloud cover allows the heat of the day to escape quickly, resulting in cold, even freezing, temperatures. The difference between the daily minimum and maximum temperatures is known as the diurnal range.

13. Extremely hot days and very cold nights: • Cloudless skiesallow the sun to heat the atmosphere very quickly to very high temperatures. At night this same lack of cloud cover means that there is no insulation to hold the heat in and it escapes very quickly to the clear night sky.

14. So night temperatures are very cold and can even drop below freezing. • Deserts have a very high DIURNAL (daily) range of temperatures, usually more than 20C. • The annual temperature ranges are also (difference between summer and winter) are also relatively high in deserts.

16. Task: Construct a climate graph for Wadi Halfa

17. Sahara desert • Rainfall less then 50 cm a year • Temperatures range from 20-25 degrees extreme maximum ranges from 43.5-49 degrees • participation is less then ten inches a year.

18. why very few clouds form in tropical deserts ? • Distance from oceans • Winds blow over large areas of land • Winds blow offshore/do not blow from sea hence no source of moisture/water sources • Low humidity • Lack of evaporation • Sparse vegetation • Lack of transpiration • High air pressure • Descending air • Cold offshore currents

19. Plants • Deserts have very little foliage, and cacti are usually scattered across the dry, barren land. • Plants that grow in the desert are just shrubs and woody trees. • Cacti store water in there bodies when it rains so they can retrieve it for later use. • Desert vegetation is scattered and spread out and almost all of the plants have spiny leaves.

20. Some Plants Include: • Barrel Cactus • Brittle Bush • ChainfruitCholla • Creosote Bush • Crimson Hedgehog Cactus • Desert Ironwood • Joshua Tree • Jumping Cholla • Mojave Aster • Ocotillo • Palo Verde • Pancake Prickly Pear Cactus • Saguaro Cactus • Soaptree Yucca • Triangle-leaf Bursage

21. Relationshipbetween the climate and the natural vegetation • Low precipitation (aridity) results in scattered (sparse) vegetation • Seeds (plants) remain dormant during long dry spells • Narrow (spiky) leaves reduce rates of evapotranspiration/because of high temperatures • Long roots (wide spreading roots) search for water • Some plants (cacti) store water in order to survive long periods of drought

22. Animals • Most of the animals that live in the desert have adapted to be able to live in the hot weather by burrowing underground during the day and only coming out at night. • Animals in the desert have also developed a unique ability to store water, which could come from the seeds they eat, or the animals they eat. • Animals are usually small nocturnal carnivores.

23. Some Animals Include: • Armadillo Lizard • Banded Gila Monster • Bobcat • Cactus Wren • Coyote • Desert Bighorn Sheep • Desert Kangaroo Rat • Desert Tortoise • Javelina • Cactus Ferruginous Pygmy Owl • Sonoran Desert Toad • Sonoran Pronghorn Antelope • Thorny Devil

24. Anteater Camel Roadrunner Gila monster (lizard) Scorpion

25. Natural environment is threatened by human activities • The area is used for farming • Animals are killed • Tourists destroy dunes • large herds of animals are grazed in the area which destroys pastures • Resources/oil is mined/drilled in the area and wildlife is killed as habitat is destroyed • The use of quad bikes/trampling on the dunes wears them away

26. South America and Africa, experience a tropical rainforest climate whilst other parts experience a tropical desert climate. • factors such as: • Latitude • Influence of overhead sun • Distance from oceans • Presence/absence of moderating influence of water body • Wind direction/trade winds/doldrums • Lack of/presence of evaporation • Presence/absence of cloud cover • Air pressure

27. References: • http://www.blueplanetbiomes.org/desert.htm • http://www.jlhs.nhusd.k12.ca.us/Classes/Science/Net_Lessons/Biomes/deserts.html#anchor32587 • http://idptv.state.id.us/dialogue4kids/season3/desert/plants.htm • http://mbgnet.mobot.org/sets/desert/tplants.html • http://www.brainpop.com/science/ecology/desert/index.weml?&tried_cookie=true

28. Thank You M. Panigrahy G.M.I.S.,Jakarta