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BIOMES
And Ecological Succession
Communities respond to disturbances
• Communities experience many types of disturbance.
– Removal of keystone species, spread of invasive species,
natural disturbances
– Human impacts cause major changes
• Resistance: community that resists change and
remains stable despite the disturbance
• Resilience: a community changes in response to a
disturbance, but later returns to its original state
– Some communities may be permanently changed.
Primary succession
• Succession: the predictable series of
changes in a community following a
disturbance
• Primary succession: disturbance eliminates
all vegetation and/or soil life
– A community is built from scratch
– Glaciers, drying lakes, volcanic lava
• Pioneer species: the first species to arrive
in a primary succession area (i.e., lichens)
– New organisms arrive, increasing
vegetation and diversity
Primary Succession
Succession
Powerpoint
Secondary succession
• Secondary succession: a disturbance dramatically
alters, but does not destroy, all local organisms
– Parts of the previous community remain and serve as
“building blocks.”
– Fires, hurricanes, farming, logging
Secondary Succession
in CT
Community change is variable
• Climax community: the community resulting from
successful succession
– Remains stable until another disturbance restarts
succession
• Community change is variable and unpredictable.
– Conditions at one stage may promote progression to
another stage.
– Organisms, through competition, may inhibit
progression to another stage.
– Other factors (e.g., soil conditions) also help determine
communities.
Succession Questions
Changed communities need to be restored
• Humans have altered Earth’s landscape to such
a degree, that no area is truly pristine.
• Ecological restoration: returning an area to
unchanged conditions
– Informed by restoration ecology: the science of
restoring an area to the condition that existed
before humans changed it
– It is difficult, time-consuming, expensive
– Best to protect natural systems from degradation
in the first place
Restoration efforts
• Prairie Restoration
– Native species replanted and invasive
species controlled http://www.prairieresto.com/mission.shtml
• The world’s largest project: Florida Everglades
– Depletion caused by flood control practices
and irrigation
– Populations of wading birds dropped 9095%.
– It will take 30 years and billions of dollars to
undo dams and diversions.
– Restoring ecosystem services will prove
economically beneficial.
http://www.dep.state.fl.us/secretary/everglad
es/
Restoration Ecology Question
Earth’s biomes
• Around the world, communities share strong
similarities.
• Biome: a major regional complex of similar
communities recognized by:
Plant type
Vegetation
structure
A variety of factors determine the biome
• The biome in an area depends on a variety of abiotic factors.
– Temperature, precipitation, ocean and air circulation, soil
• Climatograph: a climate diagram showing an area’s temperature
and precipitation
Similar biomes occur at
similar latitudes.
http://www.ucmp.berkeley.edu/exhibits/biomes/index.php
http://www.bcscience.com/bc10/docs/puzzles/section01_1_puzzle/index.html
Aquatic systems have biome-like patterns
• Various aquatic systems have distinct communities.
– Coastlines, continental shelves
– Open ocean, deep sea
– Coral reefs, kelp forests
– Coastal systems (marshes, mangrove forests, etc.)
– Freshwater systems (lakes, rivers, etc.)
• Aquatic systems are shaped by:
– Water temperature, salinity, and dissolved nutrients
– Wave action, currents, depth
– Substrate type and animal and plant life
Biome Question
Biome Question
Temperate forests
• Temperate forests occur in eastern North America, northeastern Asia, and
western and central Europe. Well-defined seasons with a distinct winter
characterize this forest biome. Moderate climate and a growing season of
140-200 days during 4-6 frost-free months distinguish temperate forests.
Temperature varies from -30° C to 30° C.
Precipitation (75-150 cm) is distributed evenly throughout the year.
Soil is fertile, enriched with decaying litter.
Canopy is moderately dense and allows light to penetrate, resulting in
well-developed and richly diversified understory vegetation and
stratification of animals.
Flora is characterized by 3-4 tree species per square kilometer. Trees are
distinguished by broad leaves that are lost annually and include such
species as oak, hickory, beech, hemlock, maple, basswood, cottonwood,
elm, willow, and spring-flowering herbs.
Fauna is represented by squirrels, rabbits, skunks, birds, deer, mountain
lion, bobcat, timber wolf, fox, and black bear.
Temperate deciduous forest
• Deciduous trees lose their leaves
each fall and remain dormant
during winter
• Mid-latitude forests in Europe, East
China, Eastern North America
• Fertile soils
• Forests: oak, beech, maple
• Fauna: squirrels, rabbits, skunks,
birds, deer, mountain lion, bobcat,
timber wolf, fox, and black bear.
Temperate deciduous forest
Temperate grasslands
• More extreme temperature
difference between winter and
summer
• Less precipitation
• Also called steppe or prairie
– Once widespread throughout
parts of North and South
America and much of central
Asia
– Much was converted for
agriculture
– Bison, prairie dogs, antelope,
and ground-nesting birds
Temperate grasslands
Temperate rainforest
• Coastal Pacific Northwest region
• Great deal of precipitation
• Coniferous trees: cedar, spruce,
hemlock, fir
• Moisture-loving animals
– Banana slug
• The fertile soil is susceptible to
erosion and landslides.
• Overharvesting has driven
species to extinction and ruined
human communities.
Temperate rainforest
Tropical forests
Tropical forests are characterized by the greatest diversity of species. They occur near the
equator, within the area bounded by latitudes 23.5 degrees N and 23.5 degrees S. One of
the major characteristics of tropical forests is their distinct seasonality: winter is absent,
and only two seasons are present (rainy and dry). The length of daylight is 12 hours and
varies little.
Temperature is on average 20-25° C and varies little throughout the year: the average
temperatures of the three warmest and three coldest months do not differ by more than 5
degrees.
Precipitation is evenly distributed throughout the year, with annual rainfall exceeding
2000 mm.
Soil is nutrient-poor and acidic. Decomposition is rapid and soils are subject to heavy
leaching.
Canopy in tropical forests is multilayered and continuous, allowing little light penetration.
Flora is highly diverse: one square kilometer may contain as many as 100 different tree
species. Trees are 25-35 m tall, with buttressed trunks and shallow roots, mostly
evergreen, with large dark green leaves. Plants such as orchids, bromeliads, vines (lianas),
ferns, mosses, and palms are present in tropical forests.
Fauna include numerous birds, bats, small mammals, and insects.
Further subdivisions of this group are determined by seasonal distribution of rainfall:
More than ½ of tropical forests have already been destroyed.
Tropical rainforest
• Central and South America,
southeast Asia, west Africa
• Year-round rain and warm
temperatures
• Dark and damp
• Lush vegetation
• Highly diverse species, but at
low densities
• Very poor, acidic soils
• Nutrients contained in plants
Tropical Rain Forest
Tropical dry forest
• Tropical deciduous
forest
• India, Africa, South
America, northern
Australia
• Wet and dry seasons
• Warm, but less rainfall
• Converted to agriculture
• Erosion-prone soil
Tropical dry forest
Savanna
• Tropical grassland
interspersed with trees
• Africa, South America,
Australia, India
• Precipitation only during
rainy season
• Water holes
• Zebras, gazelles, giraffes,
lions, hyenas
Desert
• Minimal precipitation
• Some deserts are bare, with
sand dunes (Sahara).
• Some deserts are heavily
vegetated (Sonoran).
• They are not always hot.
– Temperatures vary widely
• Saline soils (“lithosols”)
• Nocturnal or nomadic animals
• Plants have thick skins or spines.
Desert
Tundra
• Canada, Scandinavia, Russia
• Minimal precipitation
– Nearly as dry as a desert
• Seasonal variation in
temperature
– Extremely cold winters
• Permafrost: permanently frozen
soil
• Few animals: polar bears, musk
oxen, caribou
• Lichens and low vegetation with
few trees
Boreal forest (taiga)
• Canada, Alaska, Russia,
Scandinavia
• Variation in temperature and
precipitation
• Cool and dry climate
– Long, cold winters
– Short, cool summers
• Poor, acidic soil
• Few evergreen tree species
• Moose, wolves, bears,
migratory birds
Boreal forests
Boreal forests, or taiga, represent the largest terrestial biome. Occuring between 50 and
60 degrees north latitudes, boreal forests can be found in the broad belt of Eurasia and
North America: two-thirds in Siberia with the rest in Scandinavia, Alaska, and Canada.
Seasons are divided into short, moist, and moderately warm summers and long, cold, and
dry winters. The length of the growing season in boreal forests is 130 days.
Temperatures are very low.
Precipitation is primarily in the form of snow, 40-100 cm annually.
Soil is thin, nutrient-poor, and acidic.
Canopy permits low light penetration, and as a result, understory is limited.
Flora consist mostly of cold-tolerant evergreen conifers with needle-like leaves, such as
pine, fir, and spruce.
Fauna include woodpeckers, hawks, moose, bear, weasel, lynx, fox, wolf, deer, hares,
chipmunks, shrews, and bats.
Current extensive logging in boreal forests may soon cause their disappearance.
Chaparral
• Mediterranean Sea,
California, Chile, and
southern Australia
• High seasonal
– Mild, wet winters
– Warm, dry summers
• Frequent fires
• Densely thicketed,
evergreen shrubs
Resources
• http://www.blueplanetbiomes.org/mojave_de
sert.htm
• http://www.savebiogems.org/wildlands/
• http://earthobservatory.nasa.gov/Experiment
s/Biome/