Download Notes Chapter 5: Climate and Terrestrial Biodiversity

Notes
Chapter 5: Climate and Terrestrial Biodiversity
Focus Questions:
What factors influence earth’s climate?
How does climate determine where the earth’s major
biomes are found?
What are the major types of desert biomes?
What are the major types of grassland biomes?
What are the major types of forest and mountain
biomes?
How have human activities affected, the world’s desert,
grassland, forest, and mountain biomes?
Case Study
Blowing in the Wind: A Story of Connections
Wind
Vital part of planet’s circulatory system
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Distributes heat
Transports heat (P and Fe in dust)
Bad News
Dust storms in Sahara increased 5 to 10-fold since
1950.
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Climate change and overgrazing
SUV connection
Transports viruses, bacteria,
fungi, and particles of long-lived
pesticides and toxic metals.
More bad news
Some agents (perhaps fungi)
may be killing corals, FL Keys
and Caribbean
Increase in asthma in
Caribbean since 1973
Fe rich dust may trigger harmful
algal blooms, FL
Pollution and dust form China
and C. Asia blows across
Pacific Ocean reduce air quality
in W US
Mixed News
Particles from volcanic eruptions decrease global temp.
Add trace elements to soil.
Familiar Lesson
No away
Everything is connected
Wind: circulates heat, moisture, plant nutrients, long-lived
air pollutants, and soil particles
Global air circulation patterns influence climate; climate
influences plants and animals found in biomes.
I. Climate: A Brief Introduction
Weather – temp., precipitation, humidity, wind
speed, cloud cover, and physical conditions over
hours or days (see Suppl. 10).
Climate – region’s general weather patterns over
a long period of time.
Average temperature and precipitation
Latitude and elevation
Earth’s Major Climate Zones (Fig. 5-2)
Back to Ocean Currents
Solar Energy and Global Air Circulation:
Distributing Heat
Factors that contribute to local climate:
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Amount of solar radiation
Motion of the earth – rotation and revolution
Air circulation patterns
Distribution of land masses and seas
Ocean currents
Elevation of land masses
Four factors that determine global circulation
patterns.
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Uneven heating of the earth’s surface
Seasonal changes in temperature and precipitation (Fig.
5-3)
Rotation of earth on its axis
• Coriolis effect (animation)
• Cells – air movement in huge regions (Fig. 5-4)
– Prevailing winds
Coriolis Web Animation http://www.wiley.com/college/strahler/0471480533/animations/ch07_animations/animation2.html
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Properties of air, water, and land
• Cyclical convection cells circulate air, heat, and moisture
vertically (Fig. 5-5).
– Six giant cells, 3 in N hemisphere and 3 in S (Fig. 5-6)
– Leads to irregular distribution of climate patterns and
vegetation (or biomes).
Ocean Currents: Distributing Heat and Nutrients
Ocean currents affect climate of regions (Fig. 5-2)
Ocean absorbs heat, bulk near equator
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Temperature differences influence vertical movements
Temperature and winds influence horizontal movements.
Distributes heat
Distributes nutrients – upwellings (see Fig. 5-2 and Suppl. 10)
Mix Water
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Nutrients
Oxygen
Atmospheric Gases and Climate: The Natural Greenhouse
Effect
Certain gases regulate earth’s average temp.
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CO2, CH4, H2O, and N2O
Greenhouse gases cause greenhouse effect (Fig. 5-7).
Human activities increasing greenhouse effect
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Evidence and climate models indicate anthropogenic climate change.
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Alter precipitation
Shift areas where crops can grow
Raise sea levels
Change where plants and animals live (or cause extinctions)
Topography and Local Climate: Land Matters
Large bodies of water moderate climate of nearby lands
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Sea breezes
Rainshadow effect (Fig. 5-8)
Monsoons – heavy rains experienced by land masses lying north
and south of warm oceans.
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Alternating wet and dry seasons
Heating of land  low pressure  draws moisture from warm ocean
Microclimates of cities – warmer than surrounding countryside.
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Haze, smog, higher temp, lower wind speed
II. Biomes: Climate and Life on Land
Why Do Different Organisms Live in Different
Places?
Difference in climate  different organisms, esp. plants.
Biomes – large terrestrial regions characterized by
similar climate, soil, plants, and animals.
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Locations of biomes have shifted  solar output, emissions
from volcanic eruptions, and continental drift.
• 5000 y.a. Sahara Desert was a fertile grassland
• 15000 y.a. arid American SW was rainy and had many lakes.
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Compare biomes locations w/ regional climates (Fig. 5-9 and
5-2).
Biomes at the 39th parallel in NA (Fig. 3-9, p. 56)
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Influence of humans?
Major factors that determine type of biome (Fig. 3-10):
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Average annual precipitation
Average annual temperature
Soil type
Biomes are not uniform
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Communities vary, but have unique attributes
Patchiness  resources not uniformly distributed and humans
remove or alter vegetation.
Climate and vegetation vary similarly with latitude and
elevation (Fig. 5-11).
III. Desert Biomes
Deserts: Tropical, Temperate, and Polar.
General Attributes
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Evaporation exceeds precipitation; annual precipitation is low
and scattered unevenly throughout year.
Cover 30% of land surface, mostly subtropical and tropical
regions.
Largest in interior of continents, other local due to rainshadow
effect.
Little water in atmosphere, vegetation, and ground  broad
temperature swings between night and daytime.
Low rainfall and different average temperatures
determine type:
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Tropical desert (Fig. 5-12a) – like Sahara and Namib of
Africa
• Hot and dry most of year
• Few plants
• Hard wind blown surface w/ rock and sand.
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Temperate desert (Fig. 5-12b) – like Mojave and
Chihuahuan in American SW.
• Daytime temperatures in summer are high and low in winter.
• More precipitation than in tropical deserts
• Sparse vegetation, mostly shrubs, cacti, and succulent adapted
to low water availability and temperature variation.
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Polar Desert (Fig. 5-12c) – Gobi in China
• Winters, cold; summers warm or hot
• Precipitation is low
How do desert plants and animals survive?
General strategies
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Adaptive strategies to reduce thermal stress
Conserve water
Desert plants
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Drop leaves, as in mesquite and creosote
Succulent plants
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No or reduced leaves
Store water and synthesize food in fleshy tissue
Open stomata only at night
Spines guard from being eaten by herbivores
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Deep taproots as in mesquite
Widely spread, shallow roots to collect water when available.
Evergreens have waxy cuticle
Annuals, grasses and wildflowers store much biomass as
dormant seed for next rainfall.
Desert Animals
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Small, nocturnal (hiding in burrows or rocky crevices during
day).
Aestivation
Concentrate urine
Thick cuticles in insects and reptiles
Water in food and metabolic water
Drink dew droplets that accumulate an night
Desert ecosystems are fragile (Fig. 5-13).
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Soils take a long time to recover. Why?
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Slow plant growth
Low species diversity
Slow nutrient cycling
Lack of water
IV. Grasslands and Chaparral Biomes
Types of Grasslands
Grasslands, or prairies, occur mostly in the interiors of
continents too moist for deserts and too dry for forests.
Reason for occurrence
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Seasonal drought
Grazing by large herbivores
Occasional fires
Three types of grasslands: tropical, temperate, and polar
(tundra)
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Results form combinations of low precipitation and various
average temperatures
Tropical Grasslands: Savannas (Fig. 5-14a)
Savanna – tropical grassland w/ scattered clumped
trees such as acacia.
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Usu. Warm year-round w/ alternating wet and dry
seasons (graph).
Lightning and heavy grazing inhibit growth of trees and
shrubs.
It’s the birthplace of mankind
In dry locations of Africa, Australia, India, and S.A.
Fauna
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Farsighted, swift, and stealthy
• Examples: East Africa’s grazers and browsers (gazelles, zebras,
giraffes, and antelope) and their predators (lions, hyenas, and
humans).
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Large herds migrate to find food and water.
Large herbivores have evolved specialized diets to minimize
competition.
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Giraffes eat leaves and shoots from tree tops.
Elephants eat leaves and branches from lower tree parts.
Wildebeests prefer short grass.
Zebra graze on longer grasses and stems.
Flora adapted to survive drought and extreme heat
and cold.
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Deep roots that can tap into ground water.
Savannas in Africa have rapidly growing human
populations
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Rapid conversion to rangeland for cattle
Overgrazing by domesticated grazers and use of trees for
firewood  savanna to desert.
Temperate Grasslands: Fertile Soils (Fig. 5-15)
Once covered vast expanses of plains and gently rolling
hills in the interiors of NA, SA, Europe, and Asia (Fig. 514b).
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NA prairies
Steppes of Eurasia
Pampas of SA
Winters, bitterly cold; summers, hot and dry; precipitation
is fairly sparse (graph).
Drought and occasional fires inhibit growth of trees and
bushes, except along rivers and streams.
Above ground grass shoots die producing fertile soils.
Top soil is held in place by thick network of intertwined
roots.
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What effect does plowing have?
Native grasses, adapted to fires.
Temperate grasslands once covered large areas of
earth.
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Fertile soil used for crops (Fig. 5-16), cattle, and suburbanand urbanization.
Polar Grasslands: Arctic Tundra
Most of year, treeless plains are bitterly cold, swept by frigid
winds, and covered with ice and snow.
Precipitation is scant and mostly in form of snow.
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Sometimes referred to as polar desert (Fig. 5-14c).
Flora
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Thick spongy mat of low-growing plants
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Grasses
Moses
Lichens
Dwarf shrubs
Most growth occurs during 6-8 wk summer (Fig. 5-17).
Permafrost – underground soil in which captured water
stays frozen for more than two consecutive.
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During brief summer the permafrost layer keeps the melted
snow and ice from soaking into the ground.
• Waterlogged tundra forms large number of shallow lakes, marshes,
bogs, ponds, and seasonal wetlands.
• Abundant “sqeeters” and other insects serve as food for migrating
birds.
Fauna
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Adaptations such as thick fur (wolf, arctic fox, musk oxen),
feathers (snowy owl), and arctic lemmings.
Global warming  melting permafrost  release of
CH4 from soil.
Fragile because of short growing season  long
time for tundra soil to recover.
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Oil drilling, pipelines, mines, and military bases leave
scars that persist for centuries.
Alpine tundra – occur between snowline and treeline.
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Vegetation similar, but more sunlight and no permafrost.
During brief summer alpine tundra can be covered w/
wildflowers.
Temperate Shrublands: Chaparral (Fig. 5-18)
Coastal areas on land that borders deserts  longer winter
rainy season than nearby desert.
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Fogs during spring and fall reduce evaporation.
Geography: S. CA, USA; Mediterranean; C Chile; S Australia;
and SW Africa
Flora
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Dense growth
Low-growing evergreen shrubs and occasional small trees w/ leathery
leaves (reduces evaporation)
Fauna
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Mule deer
Chipmunks
Jackrabbits
Lizards
Various birds
Long, warm and dry summer  highly flammable veg.
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Fire resistant root and seed that need to be heated to germinate.
Big ecological footprint – folks like homes in nice climate
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Mild, wet winters and warm, dry summers
Fires and mudslides make these areas a risky place to live.
V. Forest Biomes
Forest biomes
Moderate to high precipitation
Trees, shrubs, and herbs
Three types result from combinations of amount of
precipitation and average temperatures.
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Tropical forests
Temperate forests
Polar (or boreal) forests
Tropical Rainforests: Threatened Centers of
Biodiversity with Poor Soils (Fig. 5-20)
Description
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Near equator
Uniformly warm temperatures year-round (Fig. 5-19a)
High humidity
Heavy rainfall almost daily
High biodiversity
Biota
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2% of the earth’s surface, but an estimated half of the planet’s terrestrial
species.
Dominated by lush broadleaf evergreen plants
No single tree dominates
Trees huge w/ shallow roots and wide bases (buttresses)
Tree tops form a dense canopy  Low light intensity on forest floor.
Ground level w/ little vegetation, but those plants found on bottom have
enormous leaves
Vines reach tree tops and form bridges between trees
Stratification of specialized plant and animal niches (Fig. 5-21)
Much of the animal life including insects, bats, and birds live in the sunny
canopy layer  abundant shelter, leaves, flowers and fruits
Ecosystem Dynamics
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High NPP
Little wind so plants rely on pollinators and seed
dispersion by animals
Decomposition of dead organic matter is rapid
Nutrients rapidly taken up and stored in plants  low
nutrients in soil
Conservation
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At least 40% of rainforests have been cleared for logging,
crops, grazing, and mineral extraction.
• Rate is increasing
• Reduces biodiversity and accelerates global warming
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Clear for crop or grazing results in:
• Only a year or two of crops
• Few nutrients in soil, leached during heavy rains.
• Areas become shrublands
Tropical Dry Forests
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Warm temperatures and wet and dry season
Trees height lower and canopies less dense
Much have been cleared for grazing and growing cops
Heavy rains cause severe erosion  few years of
productivity, then land is abandoned.
Temperate Deciduous Forest: Changing with the
Seasons (Fig. 5-22)
Description
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Moderate average temperatures, change significantly w/
season.
Long, warm summers; cold but not too severe winters
Abundant precipitation spread evenly throughout year (Fig. 519b)
Dominated by broadleaf deciduous trees, drop leaves in fall
and become dormant over winter; grow ‘em back in spring
Biota
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Broadleaf deciduous trees – oak, hickory, maple, poplar,
and beech.
Fewer species than tropical rain forests, but richer ground
layer diversity
Once home for large predators such as bears, wolves,
foxes, wildcats, and mountain lions.
Dominants mammals: white-tailed deer, squirrels, rabbits,
opossums, raccoons and rodents.
Warblers, robins and other birds migrate to these forests
during summer for the breeding season
Ecosystem Dynamics
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Slower decomposition produces a storehouse of nutrients
in leaf litter.
Production occurs in warmer months when photoperiod is
longer.
Conservation
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Large predators have been killed or displaced because of
habitat destruction.
Many migratory birds are declining because of habitat
fragmentation and destruction
These forests once covered eastern half of the US and
western Europe
• This biome has been disturbed by humans more than any other
• Agriculture, industrialization and urbanization
Evergreen Coniferous Forests: Cold Winters, Wet
Summers, and Conifers (Fig. 5-23)
Description
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Also called boreal forests pf taigas
Just south of arctic tundra
Subarctic: Winters are long, dry and extremely cold with six to
eight hours of daylight; summers are short, cool to warm and
up to 19 hours of photoperiod (Fig. 5-19c).
Plant diversity low
Biota
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Spruce, fir, cedar, hemlock, and pine that keep some of
their narrow-pointed (needles) leaves year-round
• Needle-shaped, waxy-coated leaved withstand intense cold and
drought of winter when snow blankets ground.
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Bears, wolves, moose, lynx, and burrowing rodents
Warblers and other insectivorous birds migrate there form
tropics to feed on hordes of flies, mosquitoes, and
caterpillars
Ecosystem Dynamics
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Keeping needles allows advantage during brief summers,
no time needed to grow new leaves.
Decomposition is slow because of low temp and high soil
acidity  lead to deep layer of leaf litter and needles.
During brief summer, soil becomes waterlog forming
acidic bogs, or muskegs
Southern Pine Forests
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Regions of moderate climates
Economically important
Conservation
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Tar sands being exploited in Canadian boreal forests
In southern pine forests, forests grow rapidly, cleared for
wood and converted to pine plantations  reduces plant
and animal diversity.
Temperate Rain Forests: Biodiversity Near Some Coastal
Areas (Fig. 5-24)
Also called coastal coniferous forests
Scattered in coastal temperate areas w/ ample rainfall or moisture
from dense ocean fogs.
Ocean moderates temp  winters mild, summers cool
Dense stands of large conifers (Sitka spruce, Douglas fir, and
redwoods) once dominated undisturbed areas of along west coast
of NA from n. CA to Canada
Little light reaches forest floor
Ground level frequently covered w/ mosses and ferns
VI. Mountain Biomes
Mountains: Islands in the Sky
Cover about ¼ of the lands surface
Dramatic changes in altitude, climate, soil, and vegetation
over a short distance (Fig. 5-25)
Steep slope
Islands of biodiversity surrounded by lower-elevation
landscapes transformed by human activities.
Contain the majority of world’s forests
Regulate earth’s climate
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75% of world’s freshwater stored in glaciers
Mountain tops reflect solar radiation
Biota
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Many species are endemic
Ecosystem dynamics
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Critical role in hydrologic cycle
Conservation
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Prone to erosion when veg. holding soil is removed by natural disturbances
(landslides and avalanches) or human activities (timber cutting and
agriculture).
Serve as sanctuaries for animals driven from lowland areas.
Fate of mountain ecosystems has not been a high priority despite coming
under increasing pressure from human activities.
VII. Human Impacts on Terrestrial
Biomes
Increasing Human Disturbance
10-55% of NPP is used, wasted, or destroyed.
Important lesson: NPP ultimately limits the number of consumers
(including humans) that earth can support.
60% of world’s major terrestrial ecosystems are being degraded or
used unsustainably.
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Destruction and degradation is increasing
A Survey of Our Harmful Ecological Impacts
Humans have had a number of specific harmful effects on the
world’s terrestrial biomes (Figs. 5-26, 5-27, 5-28, and 5-29).
Seasonal Changes in Temp
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Prevailing Winds
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Convection Cell
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Convection Cells in Relation to Biomes
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Greenhouse Effect
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Rainshadow
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Fig 5-2
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Fig 5-9
Biomes in NA, 39th Parallel (Fig. 3-9)
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Fig. 3-10
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Fig. 5-11
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Tropical Desert (Fig. 5-12a)
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Temperate Desert (Fig. 5-12b)
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Polar Desert (Fig.5-12c)
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North American Desert Biome (Fig. 5-13)
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Tropical Savanna (Fig. 5-14)
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Temperate Grassland (Fig. 5-14b)
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Temperate Tall-grass Prairie Ecosystem
(Fig. 5-15)
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Crops Replace Grasslands (Fig. 5-16)
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Polar Grassland, or Artic Tundra
(Fig. 5-14c)
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Arctic Tundra (Fig. 5-17)
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Chaparral Vegetation (Fig. 5-18)
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Tropical Rain Forest Ecosystem (Fig. 5-20)
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Tropical Rain Forest Climate Graph (Fig. 5-19a)
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Stratification in a Tropical Rain Forest (Fig. 5-21)
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Temperate Deciduous Forest (Fig. 5-22)
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Temperate Deciduous Forest Climate Graph
(Fig. 5-19b)
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Evergreen Coniferous Forests (Fig. 5-23)
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Evergreen Coniferous Forest Climate
Graph (Fig. 5-19c)
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Temperate Rain Forest (Fig. 5-24)
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Mount Rainier National Park (Fig. 5-25)
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