1. Succession

2. Succession Disturbances such as fires, landslides, hurricanes, and floods trigger a sequence of changes in the composition of a community. Certain species flourish immediately after the disturbance and are replaced by others etc.

3. Succession Succession is the gradual sequential growth of species in an area. There are two types of succession that are recognized. –Primary succession – The development of a community that has not previously supported life. Examples – bare rock, sand dunes, an island formed from volcanic eruption.

4. Succession –Secondary succession - The sequential replacement of species that follow the disruption of an existing community. Examples – Natural disasters, development, logging, farming, mining. –Pioneer Species – Species that predominate early succession. They tend to be small, fast growing, and hardy. Examples – ragweed, crabgrass

5. Primary Succession Often occurs slowly because the minerals for plant growth are unavailable. –Rock may take many years of repeated freezing and thawing to eventually break down. –Example is the Canadian Shield formed from retreating glaciers 12000 years ago leaving barren bedrock. –Eventually lichens formed and their decay provided nutrients for succeeding plant forms.

8. Secondary Succession Secondary succession takes about 100 years for the original ecosystem to return through well defined stages. 1.Annual grasses 2.Shrubs 3.Smaller trees such as dogwoods or pines 4.Deciduous forest

10. Stages of Succession

11. Succession The traditional description says that the community proceeds through a predictable series until it reaches a Climax community. Meaning that each stage is replaced by new species more suited to the changing community until it reaches a climax of stable individuals. Current observations indicate that succession is a continual process and climax communities may never be reached.

12. Question? How would a fire alter succession in a community?

13. Question? Why do the plants that we think of as weeds make excellent pioneer species?

14. Question? What is the difference between a pioneer species and a climax community?

15. Question? Describe the geological process of soil formation as it relates to succession.