1. Changes in Ecosystems: Ecological Succession

2. What is Ecological 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

3. Examples of Changing Ecosystems A forest could have been a shallow lake a thousand years ago. Mosses, shrubs, and small trees cover the concrete of a demolished building.

4. Ecological Succession Gradual process of change and replacement of the types of species in a community. May take hundreds or thousands of years.

5. Newer communities make it harder for the older ones to survive. Example: Younger birch trees will have a harder time competing with taller, older birch trees for sun, but a shade loving tree may replace the smaller birch trees.

6. Primary Succession Begins in a place without any soil: »Sides of volcanoes »Landslides »Flooding First, lichens that do not need soil to survive grow on rocks Next, mosses grow to hold newly made soil Known as PIONEER SPECIES

7. Pioneer Species Lichens break down rock to form soil. Low, growing moss plants trap moisture and prevent soil erosion

8. 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

10. Primary Succession Simple plants like mosses and ferns can grow in the new soil

11. Primary Succession The simple plants die, adding more organic material (nutrients to the soil) The soil layer thickens, and grasses, wildflowers, and other plants begin to take over

12. Primary Succession These plants die, and they add more nutrients to the soil Shrubs and trees can survive now

13. Primary Succession Insects, small birds, and mammals have begun to move into the area What was once bare rock, now supports a variety of life

14. Primary succession is very slow. Begins where there is no soil. Takes several hundred years to produce fertile soil naturally. First species to colonize bare rock would be bacteria and lichens.

15. Lichens Do not require soil. Colorful, flaky patches. Composed of two species, a fungi and an algae. The algae photosynthesize and the fungi absorbs nutrients from rocks and holds water. Over time, they break down the rock.

16. Primary succession can be seen happening on the sidewalks. If left alone, even NYC would return to a cement filled woodland.

17. Secondary Succession Begins in a place that already has soil and was once the home of living organisms Occurs faster and has different pioneer species than primary succession Example: after forest fires

18. Secondary Succession: Mt. St. Helens Erupted in 1980. 44,460 acres were burned and flattened. After the eruption, plants began to colonize the volcanic debris. Pioneer species: the first organism to colonize any newly available area and begin the process of ecological succession.

19. Over time, the pioneer species makes the area habitable by other species. Today, Mt. St. Helens in the process of secondary succession. Plants, flowers, new trees and shrubs have started to grow. If this continues, over time they will form a climax community.

20. Fire and Secondary Succession Natural fire caused by lightening are a necessary part of secondary succession. Some species of trees (ex: Jack pine) can only release their seeds after they have been exposed to the intense heat of a fire. Minor forest fires remove brush and deadwood.

21. Fire and Secondary Succession Some animals depend on fires because they feed on the newly sprouted vegetation. Foresters allow natural fires to burn unless they are a threat to human life or property.

25. 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

26. Climax community: the final and stable community. Climax community will continue to change in small ways, but left undisturbed, it will remain the same through time.

28. Old-field Succession Occurs in farmland that has been abandoned. Grasses and weeds grow quickly, and produce many seeds that cover large areas.

29. Over time, taller plants grow in the area, shading the light and keeping the pioneer species from receiving any light. The longer roots of the taller plants deprive the pioneer species from water. The pioneer species die.

30. Taller trees begin to grow and deprive the taller plants of water and light. Followed by slow growing trees (oaks, maples) takeover the area. After about a century, the land returns to a climax community.