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 1.Succession occurs following a disturbance in an ecosystem

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PostSubject: 1.Succession occurs following a disturbance in an ecosystem   03/03/09, 11:19 pm

• Succession- the sequence of biotic changes that regenerate a damaged community or create a community from a previously uninhabited area
• Succession created the Hawaiian islands starting over 70 million years ago

PRIMARY SUCCESSION
• Primary succession- the establishment and development of an ecosystem in an area that was previously uninhabited.
• Pioneer species- First organisms in an area. Ex- lichens and some mosses
• Pioneer species break down solid rock in the soil into smaller pieces
Usual Pattern-
• Bare rock is exposed by retreated glacier or cooled lava. Weathering forms cracks in its surface, breaking it into smaller pieces
• (0-15 years)Lichen and moss grow in the cracks, breaking up the rocks more. When they die, their remains mix with rock pieces to form a thin layer of soil
• (15-80 years) Seeds are blown in or dropped by birds, small flowers and shrubs grow. In addition to breaking up rocks and form more soil, they create a habitat for small animals
• (80-115 years) trees take root, larger animals move in
• (115-200) different trees take root in shade and replace the old trees
SECONDARY SUCCESSION
• Secondary succession- the reestablishment of a damaged ecosystem in an area where the soil was left intact
• Rebuilds ecosystem after disturbance, such as a fire or hurricane
• There is no end to secondary succession- always changing the face of the ecosystem.
Usual Pattern-
• (0-2 years)- horse weed, crabgrass, asters
• (2-18 years)- grass, shrubs, pine seedlings
• (18-70 years)- Pine forest and young hardwood seedlings
• (70-100 years)- oak hickory forest
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