7-2 Biomes Basics Deserts

8/12/2019 7-2 Biomes Basics Deserts

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BiomesDistinct ecosystems determined

by:

Latitude

Altitude

Proximity to bodies of water and

mountains


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Latitude

Tropical

Technically between 23.5o north and south,for biome purposes 30o N/S is the commonparameter.

High average temp all year

At the equator, virtually no variation in temp

Toward 30o, seasonal variations of hot andhotter


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Climate type

Cold

Cool Temperate

Warm Temperate

Tropical

(equator)

Tropical

Warm Temperate

Cool Temperate

Cold

Fig. 6.6a, p. 125


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Temperate

Between 30o

and 60o

latitude

Larger seasonal temperature variation

Warmer closer to 30o, Arizona

Cooler further from equator, Minneapolis,

Edmonton cooler still


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Polar

60o north and south to the poles 90o

Near 60o, seasonal variation (polar

forests, eventually gives way to tundra)

Close to poles, year round ice (at leastuntil recently)


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Precipitation At each region of latitude, variable precipitation

determines what type of vegetation will besuccessful.

Deserts are the driest biomes Grasslands have moderate precipitation,

but not enough to support trees as thedominant vegetation

Forests have the most precipitation,enough to support trees


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Fig. 7-10, p. 147

Cold

Polar

TundraSubpolar

TemperateConiferous forest

Desert

Deciduousforest

Grassland

Chaparral Tropical

Hot

DesertWet Rain forest Savanna

Tropicalseasonal

forest

Dry

Scrubland


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Desert Biomes NOT ALL HOT

Defined by precipitation, less than 25 cm(~ 10 inches) per year

Usually found in interior region ofcontinents, far from wet ocean air masses,also found on leeward side of mountainranges

Large daily temperature flux due to lowhumidity


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Types of Deserts Tropical desert

Form at 30o north (Sahara) and south(Namib, Kalahari) latitude as dry air

masses return to the surface afterdumping their moisture closer to theequator

Most desolate, uninhabitable places onearth, virtually no vegetation forthousands of square miles, year round

hot and dry


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Tropical Desert

Sahara and Namib in Africa as examples


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Tropical desert(Saudi Arabia)

Fig. 6.19a, p. 133


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Temperate Deserts Occur at middle latitudes

Often the result of rain shadows on theleeward side of mountain ranges

Southwest US

Seasonal variation, a little more rainfallthan a tropical desert, allows for sparsevegetation


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Temperate Desert - Examples include our

Southwest, Arizona, New Mexico


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Temperate desert(Reno, Nevada)

Fig. 6.19b, p. 133


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Polar Desert

Rare system, higher latitudes, coldwinter, hot summer shorter thanthat in temperate deserts

Gobi in Northwest China


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Cold deserts, like the Gobi in Northern China/Mongolia


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Polar desert(northwest China)

Fig. 6.19c, p. 133


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Desert Adaptation Plants

Wax coated leaves (cuticle)

Reduced leaves (needles)

Gas exchange only at night

Deep tap roots to reach groundwater and/orwide lateral root nets to catch all possible rain

Alleopathy (root toxins into soil) Dormancy, short life cycles when water

becomes available


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Desert Animal Adaptations

Small, less evaporative surface, smaller

food need Burrowing

Nocturnal (especially mammals)

Thick, waterproof skin (reptiles)

Radiators

Dry feces, urine crystals Estivation


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Human Impact on Deserts Human Population Encroachment

Irrigation, aquifer depletion, saltaccumulation

Waste storage, weapons testing Recreational vehicles

Deserts recover very slowly from

disturbance. Why?

7-2 Biomes Basics Deserts

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