Ecological Succession http://static.howstuffworks.com/gif/wildfire-deer.jpg How do ecosystems respond following a disturbance?

Vocabulary Climax Forest Lichen Pioneer Species Primary Succession Secondary Succession

ecological succession: series of changes that occur over time in an ecosystem primary succession: succession that occurs on surfaces where no soil exists secondary succession: succession that occurs following a disturbance that changes an existing community without removing the soil

Primary Succession Occurs when bare rock is exposed by a retreating glacier or created by cooled lava. – The soil is gone! pioneer species: first species to populate a previously uninhabited area (mosses, lichens)

Mosses and Lichens: Fungus/algae that can grow on bare rock

Succession progresses from pioneer species to more complex ecosystems and longer-lived trees, ultimately resulting in a Climax Community

This process may take hundreds of years from the first plants until a climax forest is reached.

Craters of the Moon National Monument Idaho, US

Craters of the Moon National Monument Idaho, US

Secondary Succession Occurs following natural or human-caused disturbances: wildfires, clearing of land for agriculture or development, wind storms, lakes that dry up, etc. The soil is still in place

Secondary succession is quicker than primary because the soil is in place. It may start with grasses as pioneer species.

South side of Mount St. Helens and Shoestring Glacier prior to the 1980 eruption. (USGS, D. Miller) http://www.fs.fed.us/gpnf/mshnvm/research/faq.html#forests

Muddy River lahar deposit following the Mount St. Helens eruption. (USDA Forest Service,  F. Valenzuela, 1981) http://www.fs.fed.us/gpnf/mshnvm/research/faq.html#forests

Fresh pyroclastic flow deposits directly north of the crater at Mount St. Helens. (USGS, 1980) http://www.fs.fed.us/gpnf/mshnvm/research/faq.html#forests

Twenty-five years later the Pumice Plain north of the crater is covered in wildflowers. (USDA Forest Service, P. Frenzen, 2004) http://www.fs.fed.us/gpnf/mshnvm/research/faq.html#forests

Mount St. Helens Washington, US Eruption May 1980 Photos taken August 2005