2. How Ecosystems Change
Primary Succession occurs on a surface where no ecosystem existed before
Secondary Succession occurs where an ecosystem previously existed—pioneer species, climax community

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7. Primary Succession

8. Ecological Succession

9. Secondary Succession
Mt St. Helen’s June 17, 1984

11. Secondary Succession
Mt. St. Helen’s August 20, 2013

12. Pioneer and Niche Species
Pioneer species are generally small hardy species that spread into un-colonized areas.
They are often perennial species that spread quickly, die off each season and leave behind a large amount of seeds for the next season.
Niche species are larger more complex organisms that live longer and interact with the surrounding environment more.
Niche species fill a biological gap where their specific traits suit their needs for survival without infringing on other species needs.

13. Climax Communities
When a barren area has been sufficiently occupied and prepared by pioneer species, the landscape develops into a climax community
Succession continues to very the biotic landscape as organisms co-evolve and adapt to the equalized state.

14. Old Field Succession