1. I can analyze the environments and the interdependence among organisms found in the world’s major biomes.
2. I can identify the environmental conditions and interdependencies among organisms found in the major biomes.
Changes in Ecosystems:
of a Forest Biome
• GLE 0607.2.4 I can analyze the
environments and the interdependence
among organisms found in the world’s
• SPI 0607.2.4 I can identify the
environmental conditions and
interdependencies among organisms
found in the major biomes.
There are two main types of
• Primary Succession: The process of
creating life in an area where no life
• Secondary Succession: The process of re-
stabilization that follows a disturbance in
an area where life has formed an
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• Natural, gradual changes in the types of
species that live in an area; can be
primary or secondary
• The gradual replacement of one plant
community by another through natural
processes over time
• The development of an
ecosystem in an area that
has never had a
community living within it
occurs by a process
• An example of an area in
which a community has
never lived before, would
be a new lava or rock
from a volcano that
makes a new island.
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• Begins in a place without any soil
– In the beginning there is only rock, sand,
– Since there is no soil, there is no community.
Why is there no soil?
In order for there to be soil there must
be nutrients like nitrogen. So … why
is there no soil?
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• Lichens begin growing on the rocks. Over
many years lichens break down rock into
• Weathering and erosion break down rock
• Lichens that do not need soil to survive
• Called PIONEER SPECIES (Why?)
• Lichens grow larger. Some die.
Decomposers arrive and break down the
lichens. The dead lichens and waste
materials of the decomposers enrich the
sand. Nitrogen cycle begins. Eventually
enough nutrients enter the sand and it
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• Seeds are blown in by the wind or carried
in by animals. Simple plants like mosses
can grow in the new soil
• The plants grow and the soil gets enriched
as plants die..
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• Herbs and weeds can grow in the thicker,
• The simple plants die, adding more
• The soil layer thickens, and grasses,
wildflowers, and other plants begin to take
• Medium sized animals and birds make this their
• The vegetation grows closer together, reducing
the amount of space available for growing.
• Competition between lichen and shrubs for the
same space. Eventually one species (lichen) will
die out (or move) and the
other species will survive
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• These plants die, and they add more
nutrients to the soil
• Shrubs and tress can survive now
• Insects, small birds, and mammals have
begun to move in
• What was once bare rock now supports a
variety of life
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• These plants die, and they add more
nutrients to the soil
• Now larger trees can grow: Beech, Oak,
The Climax Community
• A climax community is a mature, stable community
that is the final stage of ecological succession. In an
ecosystem with a climax community, the conditions
continue to be suitable for all the members of the
• Any particular region has its own set of climax
species, which are the plants that are best adapted
for the area and will persist after succession has
finished, until another disturbance clears the area.
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These are Climax Communities
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• Two main physical factors determine the nature of the
community that develops in an area. These are
temperature and the amount of rainfall.
• If we place the amount of rainfall on a graph’s “x”
axis, from 0-10, 10-20,and 20-30+ inches and the
temperature along the “y” axis from hot, moderate, to
cold, the various types of ecosystems will fit into the
graph based on the conditions that they require.
Cold Cold desert Tundra Taiga
Moderate Temperate forest Grassland Deciduous forest
Hot Hot desert Savanna Tropical forest
Rainfall (inches) 0-10 10-20 20-30+
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A summary of changes that occur during
• Pioneer species colonize a bare or disturbed site. Soil building.
• Changes in the physical environment occur (e.g., light,
• New species of plants displace existing plants because their
seedlings are better able to become established in the changed
• Newly arriving species alter the physical conditions, often in
ways that enable other species to become established.
• Animals come in with or after the plants they need to survive.
• Eventually a climax community that is more or less stable will
become established and have the ability to reproduce itself.
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• Disturbances will start the process of succession again.
• An avalanche?
Threats to Climax Communities
• Forest Fires
• Humans building cities and roads
• Flooding, Volcanic eruptions
• Clearing a community for agricultural purposes
• Anything that destroys the existing community,
but much of the soil remains. Sometimes, some
of the organisms remain as well.
• Organisms are destroyed but the soil is
• The soil already contains the seeds of
weeds, grasses, and trees. More seeds
are carried to the area by wind and birds.
• Succession begins again but the primary
species are different.
• Because soil is present, this succession is
Secondary Succession on an
• 1. Some seeds in the
soil begin to grow.
• Larger shrubs move in.
• 3. Fast growing trees
(such as pines) move
• 4. These are followed
• A stable group of plants and animals that
is the end result of the succession process
• Does not always mean big trees
– Grasses in prairies
– Cacti in deserts
• Nationwide, 70 million acres of public and private lands are
at serious risk from insects and diseases
• Across the South, one of the biggest forest management
challenges is the Southern Pine Beetle. Attacking timber
stands throughout the region, it is estimated that 57 million
acres are at risk of infestation. From 1999 to the present,
the Southern Pine Beetle outbreak has caused timber value
losses of over $1.5 billion.
Gypsy Moth, Lymantria dispar
Photo from USDA APHIS PPQ archives
• Forest pests and disease have seriously harmed the environment and have imposed
significant cost to the U.S. economy. Exotic pests and pathogens, such as the
chestnut blight, Dutch elm disease, and beech bark disease have had a profound
effect on Eastern forests.
• Management of these pests and diseases has been impacted by a variety of factors
such as forest fragmentation, increasing human population, and the expansion of
• Prompt identification and treatment of forest diseases often means the difference
between losing or saving a valuable forest stand.
Annosum Root Disease
• Invasive Plants
• Invasive species have been characterized as a “catastrophic wildfire
in slow motion.” Thousands of nonnative invasive plants have
infested millions of acres of land and water across the Nation.
• These invaders cause massive disruptions in ecosystems by
reducing biodiversity and degrading the health of our nation’s
forests, prairies, mountains, wetlands, rivers, and oceans. They
have the capacity to dominate, overwhelm, or wipe out native
• The financial impact from invasive species infestations in the United
States has been estimated at $138 billion per year in total economic
damages and associated control costs.