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How Ecosystems Change

How Ecosystems Change. Ecosystems are constantly changing. A forest hundreds of years ago might have been a shallow lake A tree falls to the ground and lets light hit the forest floor, allowing seeds to germinate Mosses and shrubs spring up in my yard if I don’t mow the lawn.

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How Ecosystems Change

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  1. How Ecosystems Change

  2. Ecosystems are constantly changing. • A forest hundreds of years ago might have been a shallow lake • A tree falls to the ground and lets light hit the forest floor, allowing seeds to germinate • Mosses and shrubs spring up in my yard if I don’t mow the lawn

  3. All these are examples of environmental change known as ecological succession

  4. Ecological succession is a gradual process of change and replacement of the types of species in a community In nature, succession may take hundreds or thousands of years

  5. Primary succession is a type of succession that occurs on a surface where no ecosystem existed before Primary succession can occur on rocks, cliffs and sand dunes

  6. Primary succession occurs in an area where no life occurred before Primary succession is slower than secondary because there is no soil

  7. The first species in primary succession are usually bacteria and lichen, which can live without soil Lichens break down rocks to help form soil

  8. Once the rocks start to break down, water gets into the cracks in the rock where it freezes and expands When bacteria and lichen die they add nutrients to the growing pile of soil

  9. Primary succession can even occur in the cracks in sidewalks Even New York City would eventually turn into a cement-filled woodland if it were not constantly cleaned and maintained

  10. Secondary succession occurs on a surface where an ecosystem has previously occurred Secondary succession is more common than primary succession

  11. Secondary succession occurs in ecosystems that have been disturbed or disrupted by: • Humans • Animals • Storms • Floods • Earthquakes • Volcanoes

  12. After an ecosystem has been disturbed, (fire flood, etc) new species begin to colonize the area These are known as pioneer species. They begin the process of ecological succession

  13. In time, pioneer species continue to grow and reproduce forming a climax community A climax community is a final and stable community

  14. Old field succession is another example of secondary succession When a farmer stops cultivating a field, grasses and weeds (pioneer species) quickly grow and cover the land

  15. Then over time, other changes occur in the area: • Grasses are replaced by shrubs (year 3-10) • Shrubs are replaced by a young pine forest (about year 20) • Finally a mature forest covers the area (about 100 years) – climax community

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