Primary succession is overgrowing of a place that was not previously occupied by vegetation. Primary successions begin where soil is absent.
In nature, primary successions are relatively rare and last for a considerable time (up to several centuries).
Example: Community formation on a bare rock, an area of solidified volcanic lava, on a newly formed sand dune, or after a glacier retreat.
Only a few plants are able to live here, they are called the pioneers of successions.
A pioneer community is a community of organisms that is formed in a place previously devoid of life for any reason.
Typical pioneers are mosses and lichens. They alter the soil by releasing acid, which breaks down and loosens stones. Dying mosses and lichens decompose under the influence of decomposing bacteria, and their remains are mixed with a loose rocky substrate (sand). This forms the first soil on which other plants can already grow.
The soil is poor in nutrients, grasses settle, which displace lichens and mosses. The roots of the grasses penetrate the cracks in the rocky rock, pushing these cracks apart and destroying the stone more and more.
Perennial plants and shrubs such as alder and willow are replacing grasses. On the roots of alder there are nodules – special organs containing symbiotic bacteria that fix atmospheric nitrogen and contribute to the accumulation of large reserves in the soil, due to which the soil becomes more and more fertile. Now trees can already grow on it, for example, pine, birch and spruce.
A successive series of communities gradually and regularly replacing each other in the succession is called a succession series.
In places where the economic activity of people does not interfere with the relationship of organisms, over time, a climax community develops.
The climax community is the final community, which is in relative accordance with the conditions of existence.
A climax community can exist for an indefinitely long time, as long as some external influence (plowing of the land, felling of forests, fire, volcanic eruption, flooding) does not disturb its natural structure.