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Title
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Ecological Succession
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Type
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Primary: Mission Briefing Article
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Operation
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Resilient Planet
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Mission:
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Mission 2: Survivors
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Print Page
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30,31
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Subjects
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Science | Earth and space science | Earth materials | Soil | Earth processes | Volcanoes | Life science | Ecosystems | Cycles | Populations | Fungi | Plants | Protists
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Grades
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5 | 6 | 7 | 8
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Keywords
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ecological, succession, Mount St. Helens, volcano, community, communities, pioneer, species, climax, eruption, ecosystem, forest, fire, flood, environment, niche, disturbance, grass, shrub, small, tree, forest, Cascade Mountain, Washington, gas, energy, mudflow, landscape, survivor, gopher, fungus, fungi, algae, fern, eruption, niche, grassland
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Duration
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00:15:00 (HH:MM:SS)
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Audience
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Teachers | Elementary Grades | Junior High
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Created On
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4/20/2008
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Copyright
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USGS, Missouri Department of Natural Resources, Sten Porse, Koyaanis Qatsi, Public Domain on Wiki Commons
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From: Resilient Planet Mission 2: Survivors (pp: 30,31) |
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Ecological Succession This article discusses how ecological succession takes place after a disturbance. It also discusses pioneer species and climax communities. |
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On the morning of May 18, 1980, Mount St. Helens, a volcano in the Cascade Mountains of Washington State, violently erupted. Its explosion of gases and pulverized rock released the energy equal to five hundred atomic bombs! The shock wave from the blast snapped trees as if they were toothpicks. Temperatures approaching 350°C (662°F) scorched nearby forests. Mudflows, more than 18 m (59 ft) high and traveling down the slopes at speeds of 161 km/h (100 mph), covered the landscape.
In an instant, entire ecological communities were destroyed. However, just below the surface, there were survivors. Beneath the ash, gophers dug their way back to the surface, mixing soil with ash. The soil contained fungus spores. The growing fungi provided an environment for algae to absorb nutrients from the ash. Algae further changed the soil’s chemistry and made it suitable for moss to grow. Then lichens joined the community. Wind blew soil into the cracks of the lava—enough for ferns to take hold. Animals visited the black lava fields to nibble on the ferns. Organic material from the plants and animals enriched the soil—creating humus and improving its ability to hold water. Wind-blown seeds could now germinate. The recolonizing of life on the slopes of Mount St. Helens is an example of ecological succession. Succession is a process that involves a series of changes in a community over time.
 Mount St. Helens before and after the 1980 eruption. The top 400 m (1,312 ft) of slope collapsed to create the largest landslide in recorded history. Ecological disruptions like volcanic eruptions, forest fires, floods, and even mowing a lawn can trigger succession. Whatever the reason, when habitats change or niches open, the process of succession can occur – even in a climax community.
The first species to arrive after a disruption tend to be small, hardy, fast growing, and able to live on very few resources. They are the pioneer species that alter the environment, creating new niches for other species to fill. As new species build the community, succession slows down. When all available niches are filled, the community stabilizes to become a climax community.
Mount St. Helens will never be the same as it was before the 1980 eruption. Through the process of succession, grasslands and forests will return and animals will come back to graze on its slopes. A new, but different, community will develop and become stable—at least until the next eruption.
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