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Unit Nine: FOREST BIOMES
Forests
• Forests cover more than 30% of Earth’s surface.
• Forests contain more than 75% of the Earth’s biomass.
• They are more diverse than any other terrestrial
ecosystem.
• The rainforest covers 6-7% of Earth’s surface, but
contains 50% of lands biomass and 70% of Earth’s
terrestrial species.
Forests
• The forest biomes are crucial to humans.
• They contain wood, the most common building
material on earth.
• However, they are an ecosystem that is in danger of
destruction due to over harvesting of resources.
I Can…
1. Describe the characteristics of the coniferous forest.
2. Explain adaptations that enable organisms to survive
in coniferous forests.
Coniferous Forests
The coniferous forest biome is primarily located in the
subarctic regions of North America, Europe, and Asia.
The summers are warm, and last from 2-4 months, while
winters are long, cold and dry.
There is little sunlight.
Precipitation falls as rain during the summer and snow
during the winter.
Coniferous Forests
The total precipitation that falls on the coniferous forest
is between 40 to 200 cm a year.
In the Southern Hemisphere, coniferous forests are found
high in mountains.
Coniferous Forests
Coniferous means cone-bearing.
Conifers are trees that produce seed cones.
Conifers have leaves called needles, which are long, thin, and
covered in a waxy substance.
Needles help the trees conserve water.
Needles are lost and replaced throughout the year, not all at
once.
Coniferous Forests
Examples:
pine, hemlock, fir, spruce, and cedar
In coniferous forests, you can often also find a few
deciduous trees, such as, aspen and birch.
Coniferous forests do not tend to be diverse. There are
usually only a few different species of trees.
Coniferous Forests
During the winter, soil moisture is frozen, so trees must
be able to survive harsh conditions.
Soils tend to be acidic due to the needles of conifers being
acidic and decomposing slowly.
The limiting factors in the coniferous forest are the harsh
winters and the nutrient-poor soils.
Coniferous Forests
Ferns, lichens, and sphagnum moss are plants that can
grow on the forest floor where there is little light.
The heavy snows that fall in the winter are important to
the forests.
The snow acts like a blanket insulating the roots of the
forest trees and preventing permafrost from forming.
Coniferous Forests
The insulating snow also allows some animals survive that
would otherwise freeze to death. Mice for example.
Many other animals are also adapted to the cold winters.
Seed eaters, such as squirrels, jays, and other rodents and
birds.
Insects are common in the summer months when the
weather is warmer.
Coniferous Forests
Large herbivores like moose, elk, beaver, and snowshoe
hares feed on plants and bark.
These herbivores are food for bears, wolves, and lynxes.
The adaptations these animals have, such as migrating,
hibernating, or living under the snow, allow them to
survive the harsh winters.
All of them have thick coats to protect them from the cold
Coniferous Forests
Large areas of coniferous forests can be found in the
northern parts of Asia and North America.
The climate in these areas is harsh, and because of this
they have not been logged off as much as other types.
The coniferous forests have been becoming more popular
for logging, but it is yet to determined how much
destruction they can sustain.
I can…
Identify the characteristics of the deciduous forest.
Describe the organisms that inhabit deciduous forests.
Deciduous Forests
In lower latitudes than coniferous forests, there exists the
temperate zone.
The temperate zone has 4 distinct seasons.
The forests are largely deciduous trees, or a tree that
sheds its leaves during a particular season of the year.
Deciduous Forests
Temperatures vary quite a bit in deciduous forests.
Temps in the summer can be as high as 30 degrees Celsius (86
F) to -30 (-22 F) in the winter.
Precipitation falls as both rain or snow, depending on the
temperature.
Deciduous forests receive between 50-300 cm of precip/year
Deciduous Forests
Deciduous trees adapt to the variable climate.
The growing season lasts 6 months, and during this time
the tree grows, produces food, and stores it for colder
seasons.
In fall, cooling temps and shortening daylight trigger the
trees to begin changing.
The trees shed their leaves and become dormant.
Deciduous Forests
The adaptation of losing leaves allows the tree to
conserve water in the cold months.
Photosynthesis stops, and the tree survives by consuming
food stored in its trunk, branches and roots.
The tree grows new leaves in spring, and photosynthesis
begins again to prepare for the next winter.
Deciduous Forests
Examples of deciduous trees include:
maple, ash, beech, oak, hickory and birch
The number of inhabitants in deciduous trees is greater
than in coniferous trees.
The deciduous forest has three distinct layers, and each
layer has its own characteristics.
Deciduous Forests
The highest section of the deciduous forest is called the
canopy.
The canopy includes the upper branches and leaves of tall
trees.
The canopy captures most of the sunlight.
Deciduous Forests
Below the canopy is the understory.
The understory is made up of trees that are younger and
shorter than those that make up the canopy.
There is also a layer of shrubs that grows in the
understory.
Deciduous Forests
At the bottom of the deciduous forest is the forest floor.
The forest floor includes mosses, ferns, and other plants
that grow on the ground.
The leaves that fall help enrich the forest soil.
The leaves decay quickly in the summer and produce
humus.
Deciduous Forests
The deciduous forests produce large amounts of food and
support a diverse community of organisms.
Fungi and other decomposers, invertebrates and insects
are common and preyed upon by birds, rodents and small
mammals.
Deer are common, but reptiles and amphibians are only
present in warmer forests.
Predators include: wolves, cougar, foxes and birds of prey
Deciduous Forests
The deciduous forests have been changed by human
activity.
The deciduous forest used to stretch across Europe, Asia,
and the eastern United States.
Only small sections of the original forest remains, due to
farming, orchards, and urban development.
Deciduous Forests
2 factors have affected the decline in the deciduous
forests
1. rich soil – the humus in deciduous forests makes
for fertile soil and great farmland.
2. hard wood – the wood is great for building uses,
and fuels.
Deciduous Forests
Some of the deciduous forests have been replanted, but a
forest ecosystem is more than just trees and cannot
simply be replanted.
The forest ecosystem takes a very long time to
regenerate.
The species that make up much of the ecosystem have
disappeared and must come back, or other species must
fill in the available niches.
Deciduous Forests
When forests are replanted, they are usually only one
species of tree and thus are not diverse.
They tend to be very productive, but have a low
biodiversity and are susceptible to disease, parasites, and
pollution damage.
I can…
Describe the characteristics of the tropical zone and of
the rain forest.
Illustrate the complexity and diversity of the rainforest
ecosystem.
Tropical Zone
The tropical zone is located near the equator.
It receives direct rays from the sun most of the year and
temperatures reach close to 77 degrees year around.
The growing season can last 12 mos., and precipitation
can be anywhere from 200-450 cm a year.
With an unchanging climate, water and temperature are
not limiting factors. Soil richness, may be, though.
Rain Forest Structure
The ever present warmth and moisture have created the
rain forest, the most diverse land biome on Earth.
Rain Forest – a dense canopy of evergreen, leafy trees,
supported by at least 200 cm of rain a year.
Over 70% of land species on Earth live in the rain forest
Although the rainforest is only 6% of Earth’s surface, it
holds 50% of the biomass.
Amazing species and biodiversity exist in the rainforest
Rain Forest Structure
There are thousands of species of trees in the rainforest.
Examples: cypress, balsa, teak, mahogany, etc.
Trees can reach heights of 50 to 60 meters!
Just like the deciduous forest, the rainforest has different,
distinct layers.
Rain Forest Structure
The first layer is the canopy, just like the deciduous forest.
The canopy captures almost all of the sunlight that falls
on the vegetation.
The vegetation on the forest floor is supported by the 1%
that does filter through the canopy.
However, the forest floor is sparse due to little sunlight.
Rain Forest Structure
There is not much organic matter to enrich the soil in the
rainforest.
The organic matter that does get to the soil is broken
down quickly in days by decomposers and taken back up
by the trees.
There are a lot of nutrients in the rainforest biome, but
most of the nutrients are part of living things and are not
contained within abiotic parts of the biome.
Rain Forest Structure
The topsoil in the rainforest is poor.
The richest soil is the top 5 cm, so trees tend to widen at
the base with ridges of wood called buttress.
Tree roots are shallow to take advantage of the nutrients
at the top of the soil.
Rain Forest Structure
Woody vines called lianas grow up the trunks of the trees
to get to the sunlight at the top of the canopy.
Other plants such as orchids and bromeliads live on the
trunks and limbs of the trees and absorb nutrients and
moisture from the air.
Rain Forest Structure
Most activity occurs in the treetops in the rainforest.
Many of the organisms are arboreal, that is they live in the
trees their whole lives.
Rainforest diversity
There are 2 reasons the rainforest is so diverse.
1. diversity in the plants
2. variety of habitats
There is such a large diversity in the plant life in the
rainforest that there is an unbelievable number of niches.
The conditions in each of the layers of the forest is so
different, that different communities inhabit each area.
Rain Forest diversity
Habitats in the rainforest differ between layers of the
forest and types of trees.
There are many connections between food webs, and
many have specialized species with complex
relationships.
Millions of different species inhabit the rainforest.
Rain Forest diversity
Scientists are not sure how many different species live in
the rainforest.
Biologist A.O. Wilson found 43 species of ant living on one
tree, and Terry Irwin estimates 50 million species of
insects on Earth, most of which live in the rain forest.
More species are found in the rainforest, making
scientists believe that there are others that we do not yet
know about.
Deforestation of the rainforest
In 1950, 10% of Earth’s surface was rainforest.
Rainforests now only cover 6% of the Earth.
Humans are using the resources and the land for more
space and to further human pursuits.
Deforestation of the rainforest
Many rainforests are in developing countries where there
is a large rate of population growth.
There is a need for land to be used for grazing, farming,
mining and living space.
The soil is poor, so after a few growth seasons there is a
need to clear more land to grow crops.
Deforestation of the rainforest
The rainforest is a vertical ecosystem, that is the habitats are all
destroyed when trees are cut down.
Scientists are very concerned about the extinction of animals in
the rainforest because of the deforestation.
If an area of the rainforest is burned, scientists think that it can
be regenerated over 100’s of years if there is rainforest around
it.
However, the diversity will be low and take many generations to
get back to levels equal that of the forest around it.
Deforestation of the rainforest
If the rainforest is bulldozed or destroyed in large
quantities, scientists think it will be unable to regenerate
and will be lost permanently.
This has become a world-wide problem due to the large
amounts of carbon that the rainforests remove from the
atmosphere.
Scientists think that rainforest destruction may account
for 25% of the rise in carbon dioxide each year.