Succession Part II

Ecosystems Unit, May 18th 2007

2 Kinds of Succession:

*Primary Succession: Succession that occurs in an area where there is no life, only rocks (e.g. succession after volcanic activity).

*Secondary Succession: Succession that occurs in an area where an ecosystem already existed (e.g. the succession of a forest after a forest fire).

Secondary succession is faster because soil and seeds are already present!

Successional Stages:

1. *Pioneer Community: The first organisms to grow on bare rock and help to form soil (e.g. lichens, small plants)

Successional Stages

2. *Intermediate Community: Organisms that live in the ecosystem once a layer of soil has developed. (e.g. grasses, shrubs, insects, birds)

Successional Stages:

3. *Climax Community: A more stable, long-lasting, complex ecosystem that changes little over time. (e.g. mature forest ecosystem)

Name the Successional Stages:

Pioneer

Community

Intermediate

Community

Climax

Community

A. B. C.

Example of Primary Succession: *Surtsey Island, Iceland.

Surtsey Island: A volcanic island (1.5 km) off of Iceland that was formed by an underwater volcanic eruption between 1963 and 1967.

Surtsey island gave

scientists an opportunity to study primary succession taking place

Succession on Surtsey Island:

At first there was no life on the island only bare lava rock and ash.

The first pioneer species to colonize the island only days after the eruption were bacteria and fungi.

Soon algae, mosses, lichen and small plants were also found. They aided in the formation of soil

Pioneer Community on Surtsey Island

Intermediate Community on Surtsey Island

Climax Community on Surtsey?

Greylag Goose

Fulmar laying eggs on moss in old craters

Over 1 million living things have been found on the island (some microscopic)!

Example of Secondary Succession: Yellowstone National Park

Yellowstone is the United State’s oldest National Park

In 1988 a severe forest fire burned 1/3 of the forest in the park

People were outraged that such a thing could be allowed to happen. Their beautiful park was destroyed!

Was the fire a good or bad thing?

Succession of Yellowstone:

Following the burn many plants such as the pink “fireweed” flourished in the rich soil and exposed sunlight.

The fire only burned between 2-6 cm into the soil so many seeds and roots survived

Succession of Yellowstone:

Lodgepole pines formed the climax community forest of the park.

The fire enabled their cones to open and shed the seeds.

Millions of new lodgepole pine seedlings were discovered growing in the park following the fire

Yellowstone 1998 (10 years after fire)

Fire is a necessary part of the forest ecosystem cycle!

Naturally, the Yellowstone area would experience a severe fire that would replace the entire forest every 100-300 yrs.

The impact of such fires are minimal:

– Animal Death: 345 dead elk (of an estimated 40,000-50,000), 36 deer, 12 moose, 6 black bears, and 9 bison died as a direct result of the fires

Scientists are now worried about climate change and its impact on the natural succession of this ecosystem