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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?