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The BiosphereClimate and Biomes
• You’ve probably heard a lot about Global Climate Change (sometimes called Global Warming).
• What is climate?
• What effects can a changing climate have on living organisms?
• Suppose your region has an especially hot summer, followed by a very cold winter that includes a snowstorm. Does this support, disprove, or have little to do with Global Climate Change?
DAILY
WORK
Climate• Climate is not the same thing as
weather!
• Climate consists of the prevailing weather patterns in a region over longs periods of time.
• Climate is caused by many factors, including location on the globe, nearness to an ocean, wind direction, geography.
90° N
90° S
NorthPole
SouthPole
0°
0°
23.5°tilt
equator
June 21st :northern summersolstice; southernwinter solstice
December 21st :northern wintersolstice; southernsummer solstice
23.5°tilt
Summer in theNorthernHemisphere
Summer in theSouthernHemisphere
The sun drives climate as well as the seasons.
• Average temperature at any part of the globe is affected not by how close we are to the sun (a common misconception) but by the angle of incidence of the sun’s rays.
Less direct rays = less solar energy =
cooler region
More direct rays = more solar energy =
warmer region
• Global air circulation influences local climates.
• Rising air cools and drops moisture.
• Descending air tends to be dry.
cool, moistair rises(rain/snow)
warm, dryair falls
PolarEasterlies
hot,moistair rises(rain)
warm, dryair falls
cool, moistair rises(rain/snow)
polar cap90 S
60 S
30 S
30 N
90 Npolar cap
cold, dryair falls
60 N
0
Westerlies
S.E.Tradewinds
N.E.Tradewinds
rainforest
desert
rotation
Westerlies
PolarEasterlies
desert
rainforest
cold, dryair falls
• According to this diagram, where on the planet should we find:
• Deserts?
• Tropical rain forests?
• Permanent snowfields?
DAILY
WORK
A. Cool, moist, rising air
B. Warm, dry,
falling air
C. Warm, moist, rising
air
• Ocean current also affect climate.
• Water tends to absorb and retain heat, and lose it slowly.
• Ocean water near the equator tends to be warm, so currents from the equator are warm.
• Water near the poles is much cooler.
• The Gulf Stream carries warm water from the equator northward, warming the coast of Europe.
• There is evidence that the Greenland ice is melting, due to Global Climate Change, and pouring cold water into the North Atlantic. If this happens what will happen to the climate of Northern Europe?
moist climate
dry climate inrain shadow
Water is carriedfrom ocean byprevailing winds.
Water is releasedas air rises andcools.
Dry air sinks,warms andabsorbs waterfrom the land.
alti
tud
e
low
high
latitude
equator(0°)
poles(90°)
deciduousforest
tundra
rock, snow, ice
coniferousforest
tropicalforest
Biomes
• The concept of “biome” is controversial.
• What “biomes” an ecology text describes depends on how fine-grained the divisions are.
• At the broadest view, there are six major biomes.
Major Biomes• Hot, dry = hot desert
• Hot, wet = tropical rain forest
• Warm, dry = grasslands
• Warm, wet = temperate deciduous forest
• Cold, dry = tundra, cold desert
• Cold, wet = northern boreal forests (taiga)
Te
mp
era
ture
Rainfall
high
high
low
low
savanna tropicalrain forest
tropicaldeciduous forest
warmgrassland
warmdesert
temperate rain foresttemperatedeciduous forest
cool grasslandcool desert
coniferous forest (taiga)
tundra
Desert
• Deserts may be hot or cold, though hot deserts have a different structure than cold deserts.
• Deserts are characterized by low rainfall.
• When rain does fall, it often falls “all at once,” and runs off.
Sagebrush Desert, Utah
Mojave Desert, California
Sahara Desert, Northern Africa
Where is this?
A dry valley in Antarctica!
Not all deserts are hot!
And even “hot” deserts aren’t always hot.
Snow in the Mojave
Tropical Rain Forest
• Characterized by a warm climate and high rainfall.
• Very high biodiversity.
• Forest structure may include multiple layers: floor, understory, canopy, and emergent layers.
• Soil layer is thin, because organic material decays quickly and is taken up by plants.
Tropical Rain Forests
Mists over a tropical rain forest
Grassland
• Grasslands, shrublands, and dry woodlands are characterized by:
• Low to moderate rainfall (semi-arid)
• Warm to hot summers, cold winters
• Prairies may have deep, rich soil
Shortgrass prairie, South Dakota
Zhongdian Steppe, Tibet
Prairie habitats are fire-based ecosystems.
Temperate Deciduous Forest
• Deciduous forests grow in temperate regions with moderate rainfall that also tend to have wet summers.
• Trees drop their leaves before the cold winters.
• The open spring canopy allows a flush of spring wildflowers before the trees leaf out again.
Mohican State Memorial Forest, Ohio
Oak-Hickory forest, Missouri
Northern Boreal Forest• Coniferous forests are favored
where there are either dry seasons or harsh winters, or both.
• Needle-shaped leaves with waxy coats can endure harsh, cold winds in northern climates and on mountains.
• Needle-leaved conifers are also found near oceans, where harsh salt spray can dry out plants.
High winter rainfall can create temperate rainforests in this biome, such as the Hoh Rainforest in
Washington.
Where there is less rainfall, the trees are more sparse, as in this taiga forest in Alaska.
Tundra
• Arctic tundra is characterized by permafrost, shrubby vegetation, and sometimes bogs.
• Alpine tundra usually does not have permafrost, but does feature alpine meadows or shrubby vegetation, and no trees.
Arctic tundra in the Arctic National Wildlife Refuge
Alpine tundra on Mt. Rainier
Ocean Biomes
• Oceans are often divided into zones just as the land is, including:
• Estuary
• Intertidal zone
• Continental shelf
• Open ocean
• Hydrothermal vents
plankton photiczone
200 m
aphoticzone
open ocean
intertidalzone
near-shorezone
Estuary
Intertidal zone: Rocky
Intertidal zone: sandy
Continental Shelf
Reef
Open Ocean
Deep Ocean
Hydrothermal Vents