Ecological Succession

Succession

• Fire, floods, volcanoes, hurricanes, and other natural disasters can change communities in a short period of time.

• Even without a disaster, communities change.• May take hundreds or thousands of years.• Succession• The natural processes by which one community of organisms

slowly replaces another in a certain area.• 2 Types• Primary• Secondary

Succession Summary

Succession

Creates new ecosystem

Restores previous

ecosystem

Example:New land created

by volcanic eruption

Example:An area

destroyed by fire

Primary Secondary

Primary Succession• Primary Succession• The series of changes that occur in an area where no

ecosystem previously existed.

• Steps• Land created by volcanic eruption or retreat of glacier• No soil present• Pioneer Species• The first organisms to live in an area.• Usually lichens or mosses that grow on rocks• Break up the rocks to form soil.

• Soil development• Seeds of plants land in new soil and begin to grow

• Several hundred-thousand years

Primary Succession

Primary Succession

Lichens• Do not require soil.• Colorful, flaky patches.• Composed of two species, a fungi and an algae.• The algae photosynthesize and the fungi absorbs

nutrients from rocks and holds water.• Over time, they break down the rock.• Lichens produce a weak acid that eats away at

the rock and breaks it down into soil

• As the rocks breaks apart, water freezes and thaws on the cracks, which breaks up the rocks further.

• When the lichens die, they accumulate in the cracks.

• Then mosses begin to grow and die, leading to the creation of fertile soil.

• Fertile soil is made up of the broken rocks, decayed organisms, water, and air.

Mosses on rocks

• Primary succession can be seen happening on the sidewalks.

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

Secondary Succession• More common• Occurs on a surface where an ecosystem has

previously existed. • Occurs on ecosystems that have been disturbed

or disrupted by humans, animals, or by natural processes such as storms, floods, earthquakes, and volcanoes.

• Occurs more rapidly than primary succession• Around 100 years

Secondary Succession

Secondary Succession

Secondary Succession: Mt. St. Helens• Erupted in 1980.• 44,460 acres were

burned and flattened.

• After the eruption, plants began to colonize the volcanic debris.

• Pioneer species: the first organism to colonize any newly available area and begin the process of ecological succession.

• Over time, the pioneer species makes the area habitable by other species.

• Today, Mt. St. Helens in the process of secondary succession.

• Plants, flowers, new trees and shrubs have started to grow.

• If this continues, over time they will form a climax community.

• Climax community: the final and stable community.

• Climax community will continue to change in small ways, but left undisturbed, it will remain the same through time.

Fire and Secondary Succession• Natural fire caused by lightening are a necessary

part of secondary succession.• Some species of trees (ex: Jack pine) can only

release their seeds after they have been exposed to the intense heat of a fire.

• Minor forest fires remove brush and deadwood.

Fire and Secondary Succession• Some animals depend on fires because they feed

on the newly sprouted vegetation.• Foresters allow natural fires to burn unless they

are a threat to human life or property.

Old-field Succession

• Occurs in farmland that has been abandoned.

• Grasses and weeds grow quickly, and produce many seeds that cover large areas.

• Over time, taller plants grow in the area, shading the light and keeping the pioneer species from receiving any light.

• The longer roots of the taller plants deprive the pioneer species from water.

• The pioneer species die.

• Taller trees begin to grow and deprive the taller plants of water and light.

• Followed by slow growing trees (oaks, maples) takeover the area.

• After about a century, the land returns to a climax community.

After Humans

When will the animal species return to the ecosystem?• You must consider what is needed for them to be

able to live in the environment.• Animal species will not return until their needs can

be met.• What do they need? A habitat that will provide

them with sufficient food, water, a hiding place, etc.

Summary Questions• How are primary and secondary succession

different?• What is a pioneer species?• Give two examples of natural disturbances and

two examples of human disturbances that can result in secondary succession.

• Grass poking through the cracks in a sidewalk is an example of succession. Is this primary or secondary succession? Explain.

Choose your favorite disaster – how will succession occur?

• A disturbance: • a forest fire • a volcano • a flood, • dried up pond • hurricane• tornado• abandoned ball field or tennis court • coral dying for lack of water