Lecture #2 Ecological Succession

1. Lecture #2 Ecological Succession Unit 7: Ecology

2. Ecological succession-the regular progression of species replacement over time in a new or disturbed community.

3. Succession shows some general trends that include: 1) Biomass increases over time. 2) An increase in the number & proportion of longer-lived species. 3) Increased species diversity. Succession on Mt. St. Helens

4. There are two types of terrestrial succession • Primary Succession • Secondary Succession

5. This colonization of new sites by communities of organisms takes place on bare rock Primary succession: The establishment and development of an ecosystem in an area that was previously uninhabited

6. New bare rock comes from 2 sources • A volcanic lava flow cools and forms rock • This is how the Galapagos islands and the Hawaiian islands formed!

7. New bare rock comes from 2 sources 2. Glaciers retreat and expose rock

8. How does the process begin? Pioneer organisms- the first organisms to colonize a newsite • Ex: lichens are the first to colonize lava rocks These guys are TOUGH! They thrive where no other species can.

9. What do they do and what happens next ? • As lichens add organic matter and form soil, mosses and other plants can colonize and grow.

10. As organic matter continues to accumulate, other species move in and change the environment further. First fast growing plants, then slower growing plants. • Over time, more and more species can find suitable niches and survive.

11. Primary succession-

12. Is there an ‘end’ to succession? Climax Community - a stable, mature community that undergoes little or no succession. ** This is not necessarily a ‘permanent’ community however. What would cause it to change?

13. Answer: A changing environment!

14. Secondary succession- Definition: Sequence of community changes that takes place when a community is disrupted by natural disaster or human actions • This type of succession occurs in areas where there HAD been previous growth. Because of this, the process is much faster than primary succession.

15. What can cause secondary succession to occur? • Forest fire • The regrowth that happens after a fire levels a portion of a forest.

16. What can cause secondary succession to occur? 2. Abandoned Agricultural Field • Native plant life from the areas surrounding the agricultural field reinvade the area.

17. Secondary succession-

18. Case Study- Yellowstone National Park 1988 – Park map showing areas (1.6 million acres) burned by the series of fires.

19. Yellowstone National Park 1988 fires – The immediate aftermath. Photo: National Parks Service

20. Yellowstone National Park • One year after the fires • Note the appearance of fireweed Photo: National Parks Service

21. Yellowstone National Park • Ten years after the fires (1998) Photo: National Parks Service

22. Yellowstone National Park • Twenty years after the fires (2008)

23. Is the Yellowstone Case study an example of primary or secondary succession?

24. Case Study - Chernobyl • In April, 1986, a nuclear power plant in the former USSR experienced a core meltdown and a catastrophic release of radioactivity into the environment.

25. Chernobyl • Surrounding towns and villages had to be immediately, permanently abandoned.

26. Chernobyl – Twenty Years Later

27. Chernobyl – Twenty Years Later Pripyat town square.

28. Chernobyl – Twenty Years Later

29. Chernobyl – Twenty Years Later A local highway.

30. Is the Chernobyl Case Study an example of Primary or Secondary Succession?

31. Take 2 minutes to describe what succession is, and to identify the similarities and differences that exist between primary and secondary succession.