Yellowstone National Park, 1988

Succession is the gradual process of community development. It involves species in one stage being replaced by different species. The time involved in succession is on a scale of tens, hundreds and thousands of years.

Succession is the gradual process of community development. It involves species in one stage being replaced by different species. The time involved in succession is on a scale of tens, hundreds and thousands of years.

Abiotic factors such as windstorms, droughts and fire can cause change in a community of plants and animals.

Biotic Factors also change communities over time. Insect epidemics can kill trees. Overgrazing can selectively remove species of plants from a forest.

Environmental disturbances have natural and man-made causes. This picture was taken in Mesa Verde, Colorado in 2000

This picture was taken after the fire. What plant life will emerge? What plants will succeed after this environmental change? Forest fires are a natural part of the life cycle of the community.

After a major change in an environment, grasses, mosses and lichens begin to colonize. It is the first step in the process of succession.

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The first species to colonize or grow in an area are called pioneer speciespioneer species. Only pioneer species are able to grow after a major disturbance in a community due to the lack of soil or nutrients. Examples: lichens and mosses

Animals begin to inhabit the area. Usually, insects appear first, then rodents and larger mammals are the last to appear.

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Opportunistic species take advantage of the work done by the pioneer species. Pioneers modify the environment in such a way that it becomes less suitable for their growth but more suitable for other species. Opportunists eventually replace pioneer species. Examples: grasses & weeds

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Over time, the decay of pioneer species, grasses and shrubs adds nutrients to the forest floor allowing more complex species to grow.

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The biodiversity of a community continues to increase as it ages. A variety of plants and animals will inhabit the area.

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Succession takes hundreds of years before completion. Species replacement continues until the community is dominated by competitively superior species. Once the community reaches a stable state of maturity it is called a climax community.

Timeline

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Lichens & Mosses

Timeline

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Grasses & Shrubs

Timeline

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Dwarf Trees

Timeline

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Immature Forest

Timeline

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Mature Forest

Timeline

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Biodiversity

Primary succession- a change in an environment where soil never existed before. Examples include recently formed volcanic lava and rock revealed when glaciers melt. Lichens and mosses first grow on the rock then soil forms from decayed mosses. Eventually, shrubs and trees follow.

Two Types of Succession

Two Types of Two Types of SuccessionSuccession

Secondary succession- a change in an environment where soil already exists. Examples include areas destroyed by forest fire, clear-cutting, or insect epidemics.

Secondary succession also occurs on smaller scales. When one giant emergent tree falls, sunlight reaches the forest floor. This brings many changes to this section of the rainforest.

More roads are being built in undeveloped areas. Farmers clear land for crops and easier access to the main road. What type of succession do new roads cause? How would it affect the plants and animals?

Deforestation in Madagascar’s rainforest: because of poor soil conditions, savannahs often form once rainforests have been cleared for crops or cattle. What type of succession is pictured here?