Ecological succession is the set of changes in community composition that occur over time in a new or disturbed communit

1. Succession after the Yellowstone fires. Succession at Mt. St. Helens. Ecological Succession Ecological succession is the set of changes in community composition that occur over time in a new or disturbed community.

2. Succession Defined: • The sequential change in the relative abundances of the dominant species in a biological community following a disturbance. • Primary succession: beginning from a abiotic environment following a cataclysmic disturbance. • Secondary succession: beginning from a major disturbance, but all forms of life are not destroyed.

3. Successional Sequence • Sere: a “unit” of succession • Seral stage: each community type within the sere • Pioneer community: the first seral stage • Seral Community: the intermediate stages • Climax community: the final seral stage • It usually takes an area 500–1000 years to go from pioneer to climax seral stages.

4. Succession is directional • The pattern of species replacement with time is not random • Seasonal changes are not succession

5. Early successional species:pioneer communities • High growth rate • Small size • Wide dispersal • Fast population growth

7. Late successional species:climax communities • Slower growth rate • Larger size • Lower rates of dispersal • Lower rates of colonization • Longer lives

9. Primary: no organics in soil Glacial retreat Volcano eruption Secondary: organics in soil Fire Logging Cultivation Disturbance leads to succession

10. Primary Succession • Succession on newly exposed or created inorganic substrate

11. Primary succession due to glacial retreat Since 1750 The world’s most rapid and extensive glacial retreat 2500 km2 ice melted Glacier Bay, Alaska

12. As the ice retreats,it leaves behind glacial till and bedrock as substrate Leaves a chrono-sequence we can study to learn about succession Glacier Bay Fjord Complex

13. Forest Succession: The gradual supplanting of one community of plants by another, usually as a result of differences in shade tolerance.

14. Secondary Succession • Succession on recently disturbed organic substrate • After a fire • After clear cut logging • After agricultural use

15. Abandoned crop land and pasture Soil ready for new plants Crabgrass established quickly Shrubs planted to jumpstart succession Old-Fields in the Piedmont, North Carolina

17. http://www.physicalgeography.net/fundamentals/9i.html

18. Animal species diversity is related to habitat availability

19. Piedmont of North Carolina http://www.env.duke.edu/forest/sucession.htm

20. Pioneer species quickly occupy a site following clearing. They grow rapidly to compete with grasses and shrubs.

21. As the crowns of pioneer species close, seedlings from these trees are unable to survive in the resulting shade.

22. Different species that have a higher tolerance to shade soon become established beneath the pioneers.

23. As the short-lived pioneers near the end of their life spans, the more tolerant trees in the forest understory begin to take over the site. The result is a major change in plant and animal species.

24. Spruce begins to take over an aspen dominated site in northern Minnesota as the short-lived pioneer aspen crowns thin with aging.

25. Beneath the second successional stage species, that often form thicker crowns than pioneers, new species that are even more shade tolerant become established.

26. The process of succession continues until the most shade-tolerant species suitable for the site (climax species) become established.

27. Seedlings of highly shade tolerant climax species thrive in the shade of their parents. Because of this, climax species will persist until disturbance sets back the succession process to the pioneer or some other stage.

28. Consider what happens following the harvest of lodgepole pine in the western U.S.

29. Clearcutting in Lodgepole pine - Montana.

30. The clearcut site looks barren immediately following harvest.

31. Similar area, two years following harvest, showing that grass has covered the site. Young pine seedlings are barely visible in the foreground.

32. At ten years following harvest young lodgepole pine trees, that have sprouted from seeds present in the soil and spread by wind and wildlife, are well established.

33. Compare this to developments following a “clearcut” by nature.

34. In early summer 1988, as today, much of Yellowstone park was covered by aging stands of lodgepole pine. Many trees had been killed by frequent outbreaks of the endemic Mountain Pine Beetle.

35. This condition led to the Great Yellowstone fire, 1988

36. Vast areas of lodgepole pine and other forest types were killed.

37. Eleven years later showed a landscape again dominated by lodgepole pine that had sprouted from seeds present in the soil.

38. Take a look at the commercial harvest of aspen in Minnesota.

39. Clearcut harvesting in Minnesota aspen.

40. Aspen harvest site one year following clear-cut harvest.

41. A good site several years following harvest. 50,000 to 100,000 stems per acre from stump sprouting.

42. Question: Assuming that 50,000 stems occupied each acre of the harvested site several years following stand establishment, what happened to the other 49,800 trees? Mature aspen stand. 65-70 years old. Approximately 200 stems/acre.

43. When reproduction of species with medium to high shade tolerance is desired following logging, selective harvest methods can be used.

44. Primary Succession at Glacier Bay, Alaska A climax community is the stable community at the final stage of succession.

45. Retreating Glaciers at Glacier Bay Alaska Make It a Natural Laboratory for Studying Primary Succession Primary succession occurs when organisms colonize a barren environment.

46. Succession Succession shows some general trends that include: 1) Biomass increase over time. 2) An increase in the number and proportion of longer-lived species. 3) Increased species diversity. Succession on Mt. St. Helens – another site of intense study.

47. Succession in a pond. © 2003 John Wiley and Sons Publishers

48. Stages of Succession • Early: plants typically small with short lifecycles (annuals…), rapid seed dispersal, environmental stabilizers. • Middle: plants typically longer lived, slower seed dispersal, and in woodland systems: larger. • Late: plants and animal species are those associated with older, more mature ecosystem. • “Climax”?

49. Fig 10.8 Graphs showing changes in biomass and diversity with succession. © 2003 John Wiley and Sons Publishers

50. Fig 10.9 Changes in soil nitrogen and phosphorus. © 2003 John Wiley and Sons Publishers