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Lesson Overview Succession
Lesson Overview 4.3 Succession
Lesson Overview Succession
Primary and Secondary Succession
How do communities change over time?
Ecosystems change over time, especially after disturbances, as some
species die out and new species move in.
Lesson Overview Succession
Primary and Secondary Succession
Ecological succession is a series of more-or-less predictable changes that
occur in a community over time.
Ecosystems change over time, especially after disturbances, as some
species die out and new species move in.
Over the course of succession, the number of different species present
typically increases.
Lesson Overview Succession
Primary Succession
Volcanic explosions can create new land or sterilize existing areas.
Retreating glaciers can have the same effect, leaving only exposed bare
rock behind them.
Succession that begins in an area with no remnants of an older
community is called primary succession.
Lesson Overview Succession
Primary Succession
For example, in Mount Saint Helens, Washington, an erupting volcano
decimated all nearby living organisms.
Changes in this community will continue for centuries.
Lesson Overview Succession
Mt. St. Helens immediately after eruption
Lake surface choked with debris
Lesson Overview Succession
Mt. St. Helens immediately after eruption
Lesson Overview Succession
Primary Succession
The first species to colonize barren areas are called pioneer species.
One ecological pioneer that grows on bare rock is lichen—a mutualistic
symbiosis between a fungus and an alga.
Lesson Overview Succession
Lesson Overview Succession
Lesson Overview Succession
Primary Succession
Over time, lichens convert, or fix, atmospheric nitrogen into useful forms
for other organisms, break down rock, and add organic material to form
soil.
Certain grasses are also pioneer species.
Lesson Overview Succession
Mt. St. Helens 15-35 years post eruption
//upload.wikimedia.org/wikipedia/commons/a/af/MSH-Fireweed.jpg
Lesson Overview Succession
Mt. St. Helens 15-35 years post eruption
Lesson Overview Succession
Mt. St. Helens 15-35 years post eruption
Lesson Overview Succession
Mt. St. Helens 35-80 years post eruption
Lesson Overview Succession
Mt. St. Helens 35-80 years post eruption
Lesson Overview Succession
Secondary Succession
Sometimes, existing communities are not completely destroyed by
disturbances. In these situations, secondary succession occurs.
Secondary succession proceeds faster than primary succession, in part
because soil survives the disturbance. As a result, new and surviving
vegetation can regrow rapidly.
Lesson Overview Succession
Secondary Succession
Secondary succession often follows a wildfire, hurricane, or other
natural disturbance.
We think of these events as disasters, but many species are adapted to
them. Although forest fires kill some trees, for example, other trees are
spared, and fire can stimulate their seeds to germinate.
Secondary succession can also follow human activities like logging and
farming.
Lesson Overview Succession
Secondary Succession
This series shows secondary succession taking place in abandoned
fields of the Carolinas’ Piedmont.
Over the last century, these fields have passed through several stages
and matured into oak forests. Changes will continue for years to come.
Lesson Overview Succession
Why Succession Occurs
Every organism changes the environment it lives in.
One model of succession suggests that as one species alters its
environment, other species find it easier to compete for resources and
survive.
For example, as lichens add organic matter and form soil, mosses and
other plants can colonize and grow.
As organic matter continues to accumulate, other species move in and
change the environment further.
Over time, more and more species can find suitable niches and survive.
Lesson Overview Succession
Climax Communities
Do ecosystems return to “normal” following a disturbance?
Secondary succession in healthy ecosystems following natural
disturbances often reproduces the original climax community.
Ecosystems may or may not recover from extensive human-caused
disturbances.
Lesson Overview Succession
Climax Communities
Ecologists used to think that succession in a given area always proceeds
through the same stages to produce a specific and stable climax
community.
Recent studies, however, have shown that succession doesn’t always
follow the same path, and that climax communities are not always uniform
and stable.
Lesson Overview Succession
Succession After Natural Disturbances
Secondary succession in healthy ecosystems following natural
disturbances often reproduces the original climax community.
Healthy coral reefs and tropical rain forests often recover from
storms, and healthy temperate forests and grasslands recover
from wildfires.
Lesson Overview Succession
Succession After Natural Disturbances
However, detailed studies show that some climax communities are not
uniform.
Often, they have areas in varying stages of secondary succession
following multiple disturbances that took place at different times.
Some climax communities are disturbed so often that they can’t really
be called stable.
Lesson Overview Succession
Succession After Human-Caused
Disturbances
Ecosystems may or may not recover from extensive human-caused
disturbances.
Clearing and farming of tropical rain forests, for example, can change
the microclimate and soil enough to prevent regrowth of the original
community.
Lesson Overview Succession
Studying Patterns of Succession
Ecologists study succession by comparing different cases and
looking for similarities and differences.
Researchers who swarmed over Mount Saint Helens after it erupted
in 1980 might also have studied Krakatau, for example.
Lesson Overview Succession
Studying Patterns of Succession
On both Mount Saint Helens and Krakatau, primary succession
proceeded through predictable stages.
The first plants and animals that arrived had seeds, spores, or adult
stages that traveled over long distances.
Hardy pioneer species helped stabilize loose volcanic debris, enabling
later species to take hold.
Historical studies in Krakatau and ongoing studies on Mount Saint
Helens confirm that early stages of primary succession are slow, and
that chance can play a large role in determining which species colonize
at different times.
Structure BookmarksSlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
FigureFigureFigureSpanSpanLesson Overview Lesson Overview
SpanSpan4.3 Succession 4.3 Succession
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Primary and Secondary Succession Primary and Secondary Succession
How do communities change over time? How do communities change over time? Ecosystems change over time, especially after disturbances, as some species die out and new species move in.
FigureFigure
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Primary and Secondary Succession Primary and Secondary Succession
Ecological succession is a series of more-or-less predictable changes that occur in a community over time. Ecological succession is a series of more-or-less predictable changes that occur in a community over time. Ecosystems change over time, especially after disturbances, as some species die out and new species move in. Over the course of succession, the number of different species present typically increases.
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Primary Succession Primary Succession
Volcanic explosions can create new land or sterilize existing areas. Volcanic explosions can create new land or sterilize existing areas. Retreating glaciers can have the same effect, leaving only exposed bare rock behind them. Succession that begins in an area with no remnants of an older community is called primary succession.
Figure
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Primary Succession Primary Succession
For example, in Mount Saint Helens, Washington, an erupting volcano decimated all nearby living organisms. For example, in Mount Saint Helens, Washington, an erupting volcano decimated all nearby living organisms. Changes in this community will continue for centuries.
Figure
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
FigureMt. St. Helens immediately after eruption Mt. St. Helens immediately after eruption
Lake surface choked with debris Lake surface choked with debris
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
FigureMt. St. Helens immediately after eruption Mt. St. Helens immediately after eruption
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Primary Succession Primary Succession
The first species to colonize barren areas are called pioneer species. The first species to colonize barren areas are called pioneer species. One ecological pioneer that grows on bare rock is lichen—a mutualistic symbiosis between a fungus and an alga.
Figure
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Figure
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Figure
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Primary Succession Primary Succession
Over time, lichens convert, or fix, atmospheric nitrogen into useful forms for other organisms, break down rock, and add organic material to form soil. Over time, lichens convert, or fix, atmospheric nitrogen into useful forms for other organisms, break down rock, and add organic material to form soil. Certain grasses are also pioneer species.
Figure
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
FigureLinkSpan
Mt. St. Helens 15-35 years post eruption Mt. St. Helens 15-35 years post eruption
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
FigureMt. St. Helens 15-35 years post eruption Mt. St. Helens 15-35 years post eruption
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
FigureMt. St. Helens 15-35 years post eruption Mt. St. Helens 15-35 years post eruption
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
FigureMt. St. Helens 35-80 years post eruption Mt. St. Helens 35-80 years post eruption
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
FigureMt. St. Helens 35-80 years post eruption Mt. St. Helens 35-80 years post eruption
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Secondary Succession Secondary Succession
Sometimes, existing communities are not completely destroyed by disturbances. In these situations, secondary succession occurs. Sometimes, existing communities are not completely destroyed by disturbances. In these situations, secondary succession occurs. Secondary succession proceeds faster than primary succession, in part because soil survives the disturbance. As a result, new and surviving vegetation can regrow rapidly.
Figure
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Secondary Succession Secondary Succession
Secondary succession often follows a wildfire, hurricane, or other natural disturbance. Secondary succession often follows a wildfire, hurricane, or other natural disturbance. We think of these events as disasters, but many species are adapted to them. Although forest fires kill some trees, for example, other trees are spared, and fire can stimulate their seeds to germinate. Secondary succession can also follow human activities like logging and farming.
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Secondary Succession Secondary Succession
This series shows secondary succession taking place in abandoned fields of the Carolinas’ Piedmont. This series shows secondary succession taking place in abandoned fields of the Carolinas’ Piedmont. Over the last century, these fields have passed through several stages and matured into oak forests. Changes will continue for years to come.
Figure
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Why Succession Occurs Why Succession Occurs
Every organism changes the environment it lives in. Every organism changes the environment it lives in. One model of succession suggests that as one species alters its environment, other species find it easier to compete for resources and survive. For example, as lichens add organic matter and form soil, mosses and other plants can colonize and grow. As organic matter continues to accumulate, other species move in and change the environment further. Over time, more and more species can find suitable niches and survive.
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Climax Communities Climax Communities
Do ecosystems return to “normal” following a disturbance? Do ecosystems return to “normal” following a disturbance? Secondary succession in healthy ecosystems following natural disturbances often reproduces the original climax community. Ecosystems may or may not recover from extensive human-caused disturbances.
FigureFigureFigure
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Climax Communities Climax Communities
Ecologists used to think that succession in a given area always proceeds through the same stages to produce a specific and stable climax community. Ecologists used to think that succession in a given area always proceeds through the same stages to produce a specific and stable climax community. Recent studies, however, have shown that succession doesn’t always follow the same path, and that climax communities are not always uniform and stable.
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Succession After Natural Disturbances Succession After Natural Disturbances
Secondary succession in healthy ecosystems following natural disturbances often reproduces the original climax community. Secondary succession in healthy ecosystems following natural disturbances often reproduces the original climax community. Healthy coral reefs and tropical rain forests often recover from storms, and healthy temperate forests and grasslands recover from wildfires.
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Succession After Natural Disturbances Succession After Natural Disturbances
However, detailed studies show that some climax communities are not uniform. However, detailed studies show that some climax communities are not uniform. Often, they have areas in varying stages of secondary succession following multiple disturbances that took place at different times. Some climax communities are disturbed so often that they can’t really be called stable.
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Succession After Human-Caused Disturbances Succession After Human-Caused Disturbances
Ecosystems may or may not recover from extensive human-caused disturbances. Clearing and farming of tropical rain forests, for example, can change the microclimate and soil enough to prevent regrowth of the original community.
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Studying Patterns of Succession Studying Patterns of Succession
Ecologists study succession by comparing different cases and looking for similarities and differences. Ecologists study succession by comparing different cases and looking for similarities and differences. Researchers who swarmed over Mount Saint Helens after it erupted in 1980 might also have studied Krakatau, for example.
SlideSpanFigureSpanSpanSpan Lesson Overview Lesson Overview
SpanSpanSuccession Succession
Studying Patterns of Succession Studying Patterns of Succession
On both Mount Saint Helens and Krakatau, primary succession proceeded through predictable stages. On both Mount Saint Helens and Krakatau, primary succession proceeded through predictable stages. The first plants and animals that arrived had seeds, spores, or adult stages that traveled over long distances. Hardy pioneer species helped stabilize loose volcanic debris, enabling later species to take hold. Historical studies in Krakatau and ongoing studies on Mount Saint Helens confirm that early stages of primary succession are slow, and that chance can play a large role in determining which species colonize at different times.