1. Changes in Ecosystems: Ecological Succession

2. Ecological Succession Ecosystems are constantly changing in response to natural and human disturbances. As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing further changes in the community. –Ecological Succession – Series of predictable changes that occurs in a community over time

3. Some Causes of Ecological Succession Can result from slow changes in the physical environment or from sudden disturbances (either natural or man made). –Some causes include: 1.Clearing land 2.Climate change 3.Introduction of nonnative species 4.Natural disasters such as volcanic eruptions, forest fires, hurricanes, & floods

4. Succession: Natural, gradual changes in the types of species that live in an area; can be primary or secondary The gradual replacement of one plant community by another through natural processes over time

5. Primary Succession Begins in a place without any soil –Sides of volcanoes –Landslides –Flooding Starts with the arrival of living things such as lichens that do not need soil to survive Called PIONEER SPECIES

6. http://botit.botany.wisc.edu http://www.saguaro-juniper.com/

7. Primary Succession Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil

8. http://www.life.uiuc.edu

9. Primary Succession Simple plants like mosses and ferns can grow in the new soil http://uisstc.georgetow n.edu http://www.uncw.edu

10. Primary Succession The simple plants die, adding more organic material The soil layer thickens, and grasses, wildflowers, and other plants begin to take over http://www.cwrl.utexas.edu

11. Primary Succession These plants die, and they add more nutrients to the soil Shrubs and tress can survive now http://www.rowan.edu

12. Primary Succession Insects, small birds, and mammals have begun to move in What was once bare rock now supports a variety of life http://p2-raw.greenpeace.org

13. Mount St. Helen Before Eruption in 1980

14. Mount St. Helen After Eruption Mount St. Helen 6 Years After Eruption Mount St. Helen 10 Years After Eruption Mount St. Helen 19 Years After Eruption

15. Secondary Succession Begins in a place that already has soil and was once the home of living organisms A disturbance of some kind changes an existing community Occurs faster and has different pioneer species than primary succession Example: after forest fires

16. http://www.geo.arizona.edu

17. http://www.ux1.eiu.edu

18. Climax Community A stable group of plants and animals that is the end result of the succession process Does not always mean big trees –Grasses in prairies –Cacti in deserts