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Ecological succession is a series of more-or-less
predictable changes that occur in a community over
time.
• Primary succession - begins in an area with no
remnants of an older community is called
• Volcanic explosions can create new land or sterilize
existing areas.
• Retreating glaciers can have the same effect, leaving
only exposed bare rock behind them.
• Secondary succession - sometimes, existing
communities are not completely destroyed.
• Secondary succession often follows a wildfire,
hurricane, or other natural disturbance.
• One ecological
pioneer species that
grows on bare rock is
lichen.
• It is a mutualistic
symbiosis made up
of fungal filaments
and green algae.
Video of Mount St. Helens
http://en.wikipedia.org/wiki/File:Summit_rim_of_Mount_St._Helens.ogv