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 StudyBlowing in the Wind: A Story of Connections

WindVital part of planet’s circulatory system

Distributes heat Transports heat (P and Fe in dust)

Bad NewsDust storms in Sahara increased 5 to 10-fold since 1950.

Climate change and overgrazing

SUV connectionTransports viruses, bacteria, fungi, and particles of long-lived pesticides and toxic metals.

More bad newsSome agents (perhaps fungi) may be killing corals, FL Keys and CaribbeanIncrease in asthma in Caribbean since 1973Fe rich dust may trigger harmful algal blooms, FLPollution and dust form China and C. Asia blows across Pacific Ocean reduce air quality in W US

Mixed NewsParticles from volcanic eruptions decrease global temp.Add trace elements to soil.

Familiar LessonNo awayEverything is connected

Wind: circulates heat, moisture, plant nutrients, long-lived air pollutants, and soil particlesGlobal 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 precipitationLatitude 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: 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.

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

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 NutrientsOcean currents affect climate of regions (Fig. 5-2)Ocean absorbs heat, bulk near equator

Temperature differences influence vertical movements Temperature and winds influence horizontal movements.

Distributes heatDistributes nutrients – upwellings (see Fig. 5-2 and Suppl. 10)Mix Water

Nutrients Oxygen

Atmospheric Gases and Climate: The Natural Greenhouse Effect

Certain gases regulate earth’s average temp. CO2, CH4, H2O, and N2O

Greenhouse gases cause greenhouse effect (Fig. 5-7).Human activities increasing greenhouse effect

Evidence and climate models indicate anthropogenic climate change.• 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 MattersLarge bodies of water moderate climate of nearby lands

Sea breezes

Rainshadow effect (Fig. 5-8)Monsoons – heavy rains experienced by land masses lying north and south of warm oceans.

Alternating wet and dry seasons Heating of land low pressure draws moisture from warm ocean

Microclimates of cities – warmer than surrounding countryside. 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.

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.

Compare biomes locations w/ regional climates (Fig. 5-9 and 5-2).

Biomes at the 39th parallel in NA (Fig. 3-9, p. 56)

Influence of humans?Major factors that determine type of biome (Fig. 3-10):

Average annual precipitation Average annual temperature Soil type

Biomes are not uniform 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

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:

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.

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.

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

Adaptive strategies to reduce thermal stress Conserve water

Desert plants Drop leaves, as in mesquite and creosote Succulent plants

• No or reduced leaves• Store water and synthesize food in fleshy tissue• Open stomata only at night• Spines guard from being eaten by herbivores

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

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). Soils take a long time to recover. Why?

• Slow plant growth• Low species diversity• Slow nutrient cycling• Lack of water

IV. Grasslands and Chaparral Biomes

Types of GrasslandsGrasslands, or prairies, occur mostly in the interiors of continents too moist for deserts and too dry for forests.Reason for occurrence

Seasonal drought Grazing by large herbivores Occasional fires

Three types of grasslands: tropical, temperate, and polar (tundra)

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.

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 Farsighted, swift, and stealthy

• Examples: East Africa’s grazers and browsers (gazelles, zebras, giraffes, and antelope) and their predators (lions, hyenas, and humans).

Large herds migrate to find food and water. Large herbivores have evolved specialized diets to minimize

competition.• 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.

Deep roots that can tap into ground water.

Savannas in Africa have rapidly growing human populations

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. 5-14b).

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.

What effect does plowing have? Native grasses, adapted to fires.

Temperate grasslands once covered large areas of earth.

Fertile soil used for crops (Fig. 5-16), cattle, and suburban- and urbanization.

Polar Grasslands: Arctic TundraMost 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.

Sometimes referred to as polar desert (Fig. 5-14c).

Flora Thick spongy mat of low-growing plants

• 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.

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 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.

Oil drilling, pipelines, mines, and military bases leave scars that persist for centuries.

Alpine tundra – occur between snowline and treeline. 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.

Fogs during spring and fall reduce evaporation.

Geography: S. CA, USA; Mediterranean; C Chile; S Australia; and SW AfricaFlora

Dense growth Low-growing evergreen shrubs and occasional small trees w/ leathery

leaves (reduces evaporation)

Fauna Mule deer Chipmunks Jackrabbits Lizards Various birds

Long, warm and dry summer highly flammable veg. Fire resistant root and seed that need to be heated to germinate.

Big ecological footprint – folks like homes in nice climate Mild, wet winters and warm, dry summers Fires and mudslides make these areas a risky place to live.

V. Forest Biomes

Forest biomesModerate to high precipitationTrees, shrubs, and herbsThree types result from combinations of amount of precipitation and average temperatures.

Tropical forests Temperate forests Polar (or boreal) forests

Tropical Rainforests: Threatened Centers of Biodiversity with Poor Soils (Fig. 5-20)

Description Near equator Uniformly warm temperatures year-round (Fig. 5-19a) High humidity Heavy rainfall almost daily High biodiversity

Biota 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 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 At least 40% of rainforests have been cleared for logging,

crops, grazing, and mineral extraction.• Rate is increasing• Reduces biodiversity and accelerates global warming

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 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 Moderate average temperatures, change significantly w/

season. Long, warm summers; cold but not too severe winters Abundant precipitation spread evenly throughout year (Fig. 5-

19b) Dominated by broadleaf deciduous trees, drop leaves in fall

and become dormant over winter; grow ‘em back in spring

Biota 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 Slower decomposition produces a storehouse of nutrients

in leaf litter. Production occurs in warmer months when photoperiod is

longer.

Conservation 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 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 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. 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 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 Regions of moderate climates Economically important

Conservation 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 forestsScattered in coastal temperate areas w/ ample rainfall or moisture from dense ocean fogs.Ocean moderates temp winters mild, summers coolDense stands of large conifers (Sitka spruce, Douglas fir, and redwoods) once dominated undisturbed areas of along west coast of NA from n. CA to CanadaLittle light reaches forest floorGround level frequently covered w/ mosses and ferns

VI. Mountain Biomes

Mountains: Islands in the SkyCover about ¼ of the lands surfaceDramatic changes in altitude, climate, soil, and vegetation over a short distance (Fig. 5-25)Steep slopeIslands of biodiversity surrounded by lower-elevation landscapes transformed by human activities.Contain the majority of world’s forestsRegulate earth’s climate

75% of world’s freshwater stored in glaciers Mountain tops reflect solar radiation

Biota Many species are endemic

Ecosystem dynamics Critical role in hydrologic cycle

Conservation 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 Disturbance10-55% 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.

Destruction and degradation is increasing

A Survey of Our Harmful Ecological ImpactsHumans 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 5-9

Fig 5-2

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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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