How are ecosystems established and reestablished after disasters? Succession How are ecosystems established and reestablished after disasters?

Primary Succession (PS) Establishment of an ecosystem where none existed previously.

Common areas where PS occurs is on solidified lava flows and sand dunes.

Pioneer Species: hardy species which first colonize an area devoid of populations. These organisms require very little nutrients, water, or soil and can be salt-resistant.

Pioneer species die and leave behind organic material that can collect moisture & particles to become soil. Larger and less hardy species are then able to colonize the area.

Eventually, there is enough soil nutrients and depth to support larger species.

These larger trees and flowering plants attract organisms with various niches.

Eventually, the ecosystem acquires enough organisms to become stable and further growth ceases. This is known as ecological climax: the last stage of succession.

Secondary Succession (SS): succession that occurs after a disaster disturbs the ecosystem. Fire, celestial impact, or volcanic eruption are possible disturbances.

SS occurs more rapidly than PS because often the disturbance does not remove soil or nutrients. Pioneer stage is not necessary. Often seedlings from large trees will germinate after disturbance.

Climax community: A community that has reached equilibrium and is no longer proceeding through succession. This community harbors sufficient flora, fauna, and other organisms to naturally arrest succession.

Plagioclimax: A climax community that exists because of human influence rather than natural progression to ecological climax.

Causes of plagioclimaxes: burning, cutting, grazing, agriculture.