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Succession and Stability

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Introduction

• Succession: Gradual change in plant and animal communities in an area following disturbance.– Primary succession on newly exposed geological

substrates.– Secondary succession following disturbance that

does not destroy soil.• Climax Community: Late successional

community that remains stable until disrupted by disturbance.

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Primary Succession at Glacier Bay

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Community and Ecosystem Stability

• Stability: Absence of change.

• Resistance: Ability to maintain structure and function in face of potential disturbance.

• Resilience: Ability to recover from disturbance.

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• Are populations organized into discrete communities?

http://soulchaser.blogspirit.com/images/medium_pdr_0249.jpg

• Humboldt hiked up Mt. Chimborazo to an elevation of 5878m.

• He recorded vegetation along the elevational gradient.

• What order?

* Ferns and palms* Grass and lichens* Oak forest* Broad-leaved herbaceous plants* Evergreen shrubs

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• Clements and others (ex. Kuchler map) felt communities were essentially superorganisms

• Are populations organized into discrete communities?

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• Clements idea of distribution

• Are populations organized into discrete communities?

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• Gleason argued for subtle transitions as opposed to sharp boundaries. He suggested a continuum.

• Are populations organized into discrete communities?