The first stage of succession involves pioneer species.
- In primary succession, pioneer plants are those that can grow without soil, such as lichens.
- Lichens begin breaking down a rock.
- Seasonal cycles of freezing and thawing form cracks in the rock.
- The dead remains of lichens and dust fall into the cracks.
- Mosses may begin to grow. When mosses and lichens die, they form parts of soil.
- Slowly, enough soil forms for small shrubs to grow.
- The roots of the shrubs break up more rock and more soil forms.
- Larger plants are able to grow.
- Eventually, a mature community exists where once there was only a bare rock.
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