ecological succession

ECOLOGICAL ECOLOGICAL SUCCESSIOSUCCESSIO

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What is Ecological Succession?

•Natural areas are subject to disturbances of many kinds. Humans and natural disturbances such as storms and fires, hurricane, earthquake etc.,

• Such disturbances have existed so long that animals and plants have adapted to them and benefit from their occurrence

• If fundamental requirements are available for life areas on earth without life are soon filled with living things.

• The Ecosystem undergo series of patterns of development called ecological succession.

• There are two types of succession– Primary succession– Secondary succession

Primary SuccessionPrimary Succession• The establishment and development

of an ecosystem in an area that was previously uninhabited

Lichensand

mosses

GrassesAnd

small shrubs

Large shrubs and small trees

Large trees

Primary Succession• Begins in a place without any soil:

»Sides of volcanoes»Landslides»Flooding

• First, lichens that do not need soil to survive grow on rocks

• Next, mosses grow to hold newly made soil

• Known as PIONEER SPECIES

Pioneer Species

Lichens break down rock to form soil.

Low, growing moss plants trap

moisture and prevent soil

erosion

Mosses on rocks

Primary Succession•Soil starts to form as lichens

and the forces of weather and erosion help break down rocks into smaller pieces

•When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil

• Primary succession can be seen happening on the sidewalks.

• If left alone, even NYC would return to a cement filled woodland.

Primary Succession• Simple plants like mosses and

ferns can grow in the new soil

Primary Succession• The simple plants die, adding

more organic material (nutrients to the soil)

• The soil layer thickens, and grasses, wildflowers, and other plants begin to take over

Primary Succession• These plants die, and they add

more nutrients to the soil• Shrubs and trees can survive

now

Primary Succession• Insects, small birds, and

mammals have begun to move into the area

• What was once bare rock, now supports a variety of life

SurtseySurtsey• The island of Surtsey formed by volcanic

eruption off of the coast of Iceland during the period from 1963 - 1967

Surtsey – Post EruptionSurtsey – Post Eruption

Surtsey TodaySurtsey Today

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Primary Succession

Secondary Succession•Begins in a place that already

has soil and was once the home of living organisms

•Occurs faster and has different pioneer species than primary succession

•Example: after forest fires

Secondary succession-

Secondary SuccessionSecondary Succession• The recovery of a damaged ecosystem in

an area where the soil was left intact

FireweedFireweedSequoia seedlingSequoia seedling

Yellowstone National ParkYellowstone National Park1988 – Devastating forest fires burn

much of Yellowstone National Park.

Yellowstone National Yellowstone National ParkPark

Yellowstone National Yellowstone National ParkPark

1988 – Park mapshowing areas

(1.6 million acres)burned by theseries of fires.

1988 fires – The immediate aftermath.Photo: National Parks Service

• One year after the fires

• Note the appearance of fireweed

• Ten years after the fires (1998)

Yellowstone National Yellowstone National ParkPark• Twenty years after the fires (2008)

ChernobylChernobyl• In April, 1986, a

nuclear power plant in the former USSR experienced a core meltdown and a catastrophic release of radioactivity into the environment.

ChernobylChernobyl• Surrounding

towns and villages had to be immediately, permanently abandoned.

Chernobyl – Twenty Years Chernobyl – Twenty Years LaterLater

Pripyat town square.


Pripyat Soccer Stadium opened in 1986.


A local highway.

Pond Succession

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The Circle of Life in Secondary Succession

PATTERNS OF SPECIES CHANGE DURING SUCCESSION

• THREE PATTERNS OF INTERACTIONS AMONG EARLIER AND LATER SPECIES OF SUCCESSION– Facilitation– Interference– Life history difference

CHRONIC PATCHES

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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 community.

• 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.

Temperature

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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• Pioneer species colonize a bare or disturbed site. Soil building. • Changes in the physical environment occur (e.g., light, moisture).

• New species of plants displace existing plants because their seedlings are better able to become established in the changed environment.

• 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. • Disturbances will start the process of succession again.

A summary of changes that occur during succession:

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Does Ecological Succession Ever Stop?

• We must recognize that any ecosystem, no matter how inherently stable and persistent, could be subject to massive external disruptive forces (like fires and storms) that could re-set and re-trigger the success ional process.

• As long as these random and potentially catastrophic events are possible, it is not absolutely accurate to say that succession has stopped.

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Does Ecological Succession Ever Stop?

• Also, over long periods of time (“geological time”) the climate conditions and other fundamental aspects of an ecosystem change.

• These geological time scale changes are not observable in our “ ecological” time, but their fundamental existence and historical reality cannot be disputed.

• No ecosystem, then, has existed or will exist unchanged or unchanging over a geological time scale.

Climax Community•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

Succession Summary

Succession

Creates new ecosystem

Restores previous

ecosystem

Example:New land

created by volcanic eruption

Example:An area

destroyed by fire

Primary Secondary

Forest Ecosystem

Environment

ecological succession