Ecological Succession Series of changes that occur during the development of an ecosystem the gradual replacement of one community by another until a.
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Ecological Succession
Ecological Succession
• Series of changes that occur during the development of an ecosystem
• the gradual replacement of one community by another until a stable long-lasting stage is reached
Changes in the Community
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What determines what the final Community will be????
• 1. Climate (temperature & moisture) and Soil Quality
• 2. In the U.P., the climate is pretty much the same, so differences in soil type influence the community type.
Four Basic Communities
• A. Pine
• B. Boreal Forest
• C. Northern Hardwoods
• D. Bog/Swamp
Why does Succession Happen?
• Each community alters the physical features of a site making it less favorable for its members and more favorable for competitors.
• In other words, each community brings about its own demise.
How long does Succession Take?
• Succession depends on the size of the ecosystem but generally takes hundreds to thousands of years.
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Types of Succession• Primary Succession – soil building occurs
on previously uninhabited site
• Examples:– Bare rock lichen moss herbs trees– Sand dune grass blueberry
cherry/poplar trees
Pioneer Species
• The first species to occupy a bare site
• Characteristics: - tough (can endure extremes of temperature - lack of moisture - lack of nutrients
Secondary Succession• Occurs on a site on which the established
community has been removed (soil already present)
• Disturbances include: – Fire (commonly used to control undergrowth)– Farming– Logging– Over-grazing– Urbanization
Climax Community
• The eventual community that occupies the site after the disturbance – it will remain that way unless it is disturbed.
• If a forest is removed, secondary succession begins with perennial weeds, poplar and cherry trees, and sometimes pine. Often fireweed is an indicator species of the stage.
• If the disturbance is severe enough, it may set it back to primary succession – may take a tremendously long time for climax community to be reached.
• In general, as succession proceeds, food chains are replaced by food webs, there is more biomass and species diversity, and the ecosystem is more stable – what might destroy an early stage does not cause as great an effect at later stages
Make Up of a Community
• Depends on tolerances of the species involved
• Tolerance– 1. Shade tolerant species – can photosynthesize
adequately at very low levels of light ex. Maple, oak seedlings, certain species of fern
– 2. Shade intolerant species – require bright light to photosynthesize enough to survive ex. Cherry, poplar, grass
How Does Succession Happen?
• Cherry/poplar seedlings colonize a disturbed site. As they grow, they shade the ground. Young cherry and poplar seedlings cannot grow in the shade but oak/maple seedlings thrive there. Eventually, oaks/maples shade the cherry and poplar trees, reducing the light to below the compensation intensity, and those trees die.
Indicator Species
• Species that live only in certain stages of succession or under very specific conditions
• Examples:– Yew – an evergreen shrub found
only in mature hardwood forests– Sphagnum moss – found only in
bogs and swamps
Disclimax Community
• Artificial communities that are maintained only by constant intervention by man ------ they are never allowed to reach the climax stage of succession
• Examples: park, farmer’s field, lawn
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are needed to see this picture.
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are needed to see this picture.
Ecotone• The transition zone
between two adjacent communities
• Example: Where a field blends into a forest -often there is a greater diversity of life in an ecotone, because the more tolerant species from each community can be found there
The End
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