Download Predator-prey interactions: lecture content

Terrestrial biomes of the world
Lecture Topics:
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Biome concept
Biome classification, distribution
Biome climate patterns (Walters Diagrams)
Biome survey/distinctive ecological
characteristics
Introduction to biome concept
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Classification systems
 Holdridge’s
Life Zone system
 Whittaker’s classification scheme based on annual
precipitation, temperature (nine biomes recognized)--simpler
for purposes here of describing basic biomes
Robert Whittaker’s classification of
biomes, based on annual precipitation,
temperature
Global distribution of biomes
Walter climate diagram: generic
Ecosystem waterlimited if temperature
line (red) exceeds
precipitation line (blue)
White zone denotes
frozen conditions,
inhospitable for life
Effective growing season
(temperature above 0 ºC)
Temperate seasonal forest biome
Temperate forest physical environment
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Found at temperate latitudes, typically 40-60º latitude
Climate highly seasonal:
 Cool
winter & warm summer, plentiful precipitation all year
 Cold makes water unavailabledeciduous foliage (leaf drop),
brilliant fall colors (depending on species)
 Spring flush of leavesabundant herbivores (caterpillars,etc.)
and migratory birds that feed on them
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Vernal herbs flower in spring, where forest floor warms up
before trees leaf-out (e.g., sweet white violet)
Different subtypes of biome
 Northern
hardwoods—e.g., sugar maple, yellow birch
 Southern hardwoods—oaks, sweet gum, tulip poplar, &
evergreens (magnolias, live oak, and pines).
 Southern pinewoods on poor, sandy soils; fire important
Examples of temperate seasonal forest
Louisiana examples: Bottomland hardwoods, upland mixedmesophytic (coniferous & deciduous) forest
Temperate rain forest
Temperate rainforest characteristics
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Found at temperate latitudes, typically 40-60º
(Northwestern U.S., S. Chile, E. Australia, New Zealand)
Climate moderately seasonal:
 Mild
winter (below freezing) versus warm to hot summer,
 Abundant winter rain
 Summer fog
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Plants dominated by giant needle-leaved trees (in U.S.:
redwoods, western hemlock, douglas fir, western cedar)
 Ancient,
formerly widespread forest type
 Why giant trees? Year-round growing season, abundant
moisture, strong potential evapotranspiration all contribute
Examples of temperate rainforest plants
Temperate grassland/desert
Physical environment of temperate
grassland/desert biome
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Typically 25-50º N, S of equator
Climate characterized by high rate evaporation (often warm
temperatures), & periodic severe (summer) droughts
 Rainfall
25-70 cm annually, too little to support forest
 Often subject to fire—e.g., prairie , longleaf pine (essentially
prairie with scattered pine trees)
 Steppes are cold deserts, dominated by shrubs & grassland
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Plants—1º productivity proportional to rainfall
 Grasses
dominate (because they’re competitive over trees where
fire, grazing predominate)
 High degree spatial heterogeneity in plants, due to topography,
soils, fire history, animal activity (e.g., prairie dogs, bison)
Examples of temperate grassland/desert
vegetation
(also known as shrub-steppe)
Woodland/shrubland
Physical environment & plants
of woodland/shrubland biome
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Location (30-40º N, S of equator)
 Mediterranean
region, coastal California, Chile,
southern S. Africa, south-western Australia
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Climate “Mediterranean” (mild, wet winter; hot, dry
summer = drought)
Plants
 Fire
adapted, dense evergreen shrubs
 Often deeply rooted, to get at scarce (summer) water
 Sclerophyllous (waxy, drought-resistant) leaves
 Aromatic compounds that dissuade insect herbivores
Examples of woodland/shrubland
vegetation
Vegetation type also known as matorral (Chile)
Subtropical desert
Physical characteristics of deserts
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Evaporation exceeds precipitation (rainfall <30 cm)
20-30º N & S Latitude (subtrop. high pressure zone)
Plants adapted to drought (= xerophytes)
 Small
leaves dissipate heat, large edge:area ratio
 Water-storage mechanisms (e.g., many cacti)
 Conserve H2O (e.g., CAM photosynthesis, waxy cuticle)
 Protected against herbivores—spines, aromatic compounds
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Diverse life-forms of desert plants:
 Succulents
(e.g., saguaro & barrel cactus) store water
 Ephemerals (annuals) grow rapidly, seed after a rain
 Phreatophytes (e.g., mesquite, palo verde) deeply rooted
 Opportunistic perennials (ocotillo) flush leaves, flower after
rain
Boreal forest
Boreal (northern coniferous) biome
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Climate & setting
 Found
typically from 50-70º N. Latitude (taiga), south in mts.
 Cold winter, cool-warm summer, 3-5 mo. growing season
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Taiga (russian for “land of little sticks”) forms continuous
stretches of boreal forest, dominated by trees in species of
spruce (Picea), fir (Abies); also known as “spruce-moose”
biome
 Diversity
of trees low (1-2 spp./site)
 Conifers dominate (tolerate cold, photosynthesize whenever
it’s warm enough, conical shape sheds snow with minimal
branch breakage)
Boreal forest vegetation
Tundra biome
Tundra physical environment & plants
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Climate & setting
 Too
cold, windy for trees; short growing season (50-60 days
in arctic, up to 180 days in alpine zones at higher elevation)
 Precipitation generally < 25 cm annually (cold air holds little
moisture), “locked up” as snow (unavailable to plants)
 Only in N. hemisphere, north. edge of all northern continents
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Plants—grassland & mixed shrubland (some dwarf trees)
 Often
low to ground = warmest microclimate, out of wind
(e.g., cushion plants)
 Lichens often important ground (& rock) cover, important in
creating soils by breaking down rocks; alders (Alnus) can be
an important nitrogen-fixer
 Northern bogs characteristic of the wettest spots—dominated
by carnivorous plants (animal source of N)
Some plants of tundra biome
Tropical rainforest biome
Climate & setting Tropical rainforest
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Near equator
Climate continuously favorable for intense biological
activity (abundant rainfall, >400 cm, & high temperatures)
 Biological
interactions (ecologically, evolutionarily) impt.
 Biological diversity staggering (latitudinal diversity gradient)
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Diverse plant life forms: trees, shrubs, epiphytes, epiphylls,
vines, lianas (woody), ferns, tree ferns
 Layering
of plants prominent: ground layer, shrubs, subcanopy, continuous canopy, & “emergents” (up to 60 m tall)
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Some plant adaptations:
 Buttresses
to help prop up often shallow-rooted trees (why?)
 Oval, waxy leaves with drip-tips (why?)
 Nutrient scavenging & extremely tight nutrient cycling
Some plants of tropical rainforest biome
Tropical seasonal forest biome
Tropical seasonal forest/savanna
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Tropical seasonal forest occurs at higher latitudes than
rainforest (10-20º N, S)
Rainfall less than rainforests (240-400 cm), highly seasonal
 3-6
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month dry season, often with no rainfall
Dry forests have almost as diverse plant and animal
communities as rainforests
 Trees
typically drought-deciduous (facultative)
 Ant-acacia mutualism is characteristic of dry forests of
Central America
 Biome highly threatened by human activities, because of its
potential for agriculture, grazing
Some trees of tropical savannas
Acknowledgements:
Some illustrations for this lecture from
R.E. Ricklefs. 2001. The Economy of
Nature, 5th Edition. W.H. Freeman and
Company, New York.