Ecology
Biomes
M. Saadatian
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1
World Biomes
Tropical Rain forest
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Distribution of biome
• The tropical rainforest is found between 10 ° N and
10 ° S latitude at elevations below 1,000 m. There are
three major, disjunct formations:
• Neotropical (Amazonia into Central America)
• African (Zaire Basin with an outlier in West Africa;
also eastern Madagascar)
• Indo- Malaysian (west coast of India, Assam,
southeast Asia, New Guinea and Queensland,
Australia.
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Distribution
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Climate
• The tropical rainforest is a forest of tall trees in a
region of year-round warmth. An average of 1250 to
6600 mm of rain falls yearly.
• The temperature in a rainforest rarely gets higher
than 34 °C or drops below 20 °C; average humidity is
between 77 and 88%. There is usually a brief season
of less rain. In monsoonal areas, there is a real dry
season. Almost all rainforests lie near the equator.
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Soil
• The soil is infertile, deeply
weathered and severely
leached. Rapid bacterial decay
prevents the accumulation of
humus. The concentration of
iron and aluminium oxides
gives the soil a bright red
colour and sometimes
produces minable deposits
(e.g., bauxite). On younger
substrates, especially of
volcanic origin, tropical soils
may be quite fertile.
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Plants I
• A tropical rainforest
has more kinds of
trees than any other
area in the world.
Scientists have
counted about 100 to
300 species in one 1hectare area in South
America. Seventy
percent of the plants
in the rainforest are
trees.
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Plants II
• All tropical rainforests resemble one another in
some ways. Many of the trees have straight trunks
that don't branch out for 100 feet or more. There
is no sense in growing branches below the canopy
where there is little light. The majority of the trees
have smooth, thin bark because there is no need
to protect them from water loss and freezing
temperatures. It also makes it difficult for
epiphytes and plant parasites to get a hold on the
trunks. The bark of different species is so similar
that it is difficult to identify a tree by its bark.
Many trees can only be identified by their flowers.
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Kapok tree
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Brazil nut
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Rubber tree
Ruffled Fan palm
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Orchids
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Bromeliad
Fern tree
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Carnivorous plants
Venus Fly Trap
Pitcher plant or Monkey Cup
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Plants III (growth forms)
• Epiphytes: the socalled air plants grow
on branches high in
the trees, using the
limbs merely for
support and
extracting moisture
from the air and
trapping the constant
leaf-fall and windblown dust.
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Plants IV (growth forms)
• Lianas: woody vines
grow rapidly up the
tree trunks when
there is a temporary
gap in the canopy
and flower and fruit
in the tree tops.
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Plants V (growth forms)
• Climbers: greenstemmed plants that
remain in the
understory. Many
climbers, including the
ancestors of the
domesticated yams
(Africa) and sweet
potatoes (South
America), store
nutrients in roots and
tubers.
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Plants VI (growth forms)
• Stranglers: these
plants begin life as
epiphytes in the
canopy and send
their roots
downward to the
forest floor.
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Fungi
• Fungi can live on the forest floor because they do
not need sunlight for growth.
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Plants VIII
• Rainforests now cover less than 6% of Earth's land
surface. Scientists estimate that more than half of all
the world's plant and animal species live in tropical
rainforests. Tropical rainforests produce 40% of
Earth's oxygen.
• About 1/4 of all the medicines we use come from
rainforest plants. More than 1,400 varieties of
tropical plants are thought to be potential cures for
cancer.
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Animals
• Animal life is highly diverse. Common
characteristics found among mammals and birds
(and reptiles and amphibians, too) include
adaptations to an arboreal life (for example, the
long tails of New World monkeys), bright colours
and sharp patterns, loud vocalizations, and diets
heavy on fruits.
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Insects
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Amphibians and reptiles
Constrictor Python
Tree frogs
Chameleon
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Birds
Harpy Eagle
Macaw
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Paradise bird
Mammals
Sloth
Tapir
Howler Monkey
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People I
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People II
• Farming: huge tracts of rainforest are cleared for
large-scale commercial plantations or livestock
ranching. Ironically, rainforest soil is useless to
humans. Rainforest soils are notoriously poor and
cannot support human agriculture for more than a
few years. Crops may grow well at first, mostly
subsisting on the minerals released when the
forest is burnt. But these minerals wash away
quickly without the protection of the thick forest
canopy and the soil soon becomes useless.
• Humans destroy by collecting and killing wild
animals and plants.
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People III
• Rainforest is also cleared to make way for homes
for people, and infrastructure like dams, roads,
electrical and communications installations.
• Rainforests are dug up as we mine for oil, gold and
other minerals. Small scale gold prospectors use
mercury which is toxic to extract gold.
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People IV
• Logging of trees for building materials, firewood,
paper products. Rainforests contain 50% of global
standing timber. Unlike the faster-growing
temperate timber trees, rainforest trees take
decades to reach economic size so it is not easy to
harvest them in a sustainable manner. Logging
roads usually allow other commercial exploitation
to follow.
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People V
• Humans kill by breaking up a rainforest into smaller
clumps. It destabilises the forest interior:
temperature and humidity are no longer constant.
Such fluctuations kill plants and animals adapted
only for stable conditions. If the fragment is too
small, it can't withstand natural seasonal changes. It
also prevents natural movement of plants and
animals from one part of the forest to another.
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Tropical Dry Forest
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Imperative Information
Temperature
Precipitation
•Temperatures are high all year: the average temperature is •The dry season is far longer than the brief period of rainfall
above 24°C
•There is no set amount of rain, it depends on the area
•Because of its proximity to the coast, fluctuations in annual
•Annual rainfall is anywhere from 10-20 cm to 1000 – 1500
temperatures are only 10-15° C
cm per year depending on the specific tropical dry forest
•Frost and temperatures below freezing are rare
•There is decreasing summer precipitation
•Temps. have been recorded as low as 3°C and as high as
31°C
• The air changes from moist due to inter-tropical region
mixtures in the summer to the dry air because of a
subtropical weather front during the winter
Solar Isolation
• Seasonal alternation
•A well defined dry season, but a short wet season in
comparison to a tropical rain forest
•The dry season typically lasts from June through August
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Limiting Factors
•Its well defined dry season limits plant growth and the
activity of animals
•A large soil-water shortage occurs, especially severe during
the hottest time prior to the rains
Species Diversity
Plant Life
•
Most of the trees and shrubs found in this
type of habitat are deciduous, losing their
leaves at beginning of the dry season
–
•
•
•
•
•
Leaves shed in dry season to conserve soil
moisture.
Up to 40 tree species in small forests
Dry forests consist of trees, shrubs, and
undergrowth of different heights which form
a canopy
Lotus, ironwood, and acacias
Columnar, jumping cholla and barrel cactus
More light penetration and more understory
vegetation than a tropical rain forest
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Animal Life
•
Tasmanian devil
•
American alligator
•
Merriam's Kangaroo rat
•
Ants
•
Lizards
•
Shrews
•
Coyotes
•
Kit and gray foxes
•
Ringtails
•
Raccoons
•
Skunks
•
Badger
•
Bobcat
•
Mountain lion
•
Ocelot
Food Chain
Energy from
sun
First tropic
level:
Producers
Second tropic
level:
Primary
consumers
heat
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heat
Third tropic
level:
Secondary
consumers
heat
Fourth tropic
level: Tertiary
consumers
Decomposers
heat
heat
Climate / Seasons:
Tropical dry forests have a seasonal
climate, alternating between a wet and dry
season. However, the dry season is often
longer than the wet season, lasting over
five months every year.
Precipitation:
The annual rainfall is
usually around 150-200
cm.
Soil:
The soil in this area is
richer with nutrients, but is
more vulnerable to erosion.
Geography:
Located from 10º to
25º N and S.
Temperature:
The annual mean temperature is
approximately 81ºF, or around 27ºC.
However, in the dry season, this may
increase to 99ºF, or 37ºC.
Sunlight:
Trees are not as close to
each other as in a rain forest,
therefore allowing more sunlight
to reach the forest floor.
Limiting Factors of the Biome:
The fact that the dry season lasts longer than the wet season, as
well as the soil’s high susceptibility to erosion, limits the growth of
certain plant life. This, in turn, will limit the biome’s ability to sustain
animal life.
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Sun
Deciduous shrubs
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Jackrabbit
Coyote
Ants
Fungus