2. Ecological Succession
How New Ecosystems Develop

3. Ecological Succession
Succession refers to the normal, slow changes that occur in the community that live in an area.
The predictable way in which an ecosystem develops over time.
Succession occurs differently in different places.

4. Ecological Succession
Ecological succession can be classified in two ways:
Primary Succession
Secondary Succession

5. Primary Succession
Primary succession begins in an area that was previously without life.
Involves the interaction of soil, microorganisms, plants and animals to establish or restore populations in areas that are void of living things.
It starts with lichens.
Lichens are a mixture
of fungi and bacteria.
Pioneer Species

6. Pioneer Species
These pioneer species are the first to inhabit an area.
Examples: Lichens, Mosses
These organisms will modify or change the environment (by forming soil, etc.) and eventually the habitat becomes favorable to other species.
Start recovery following a disturbance in BOTH primary and secondary succession. In primary, pioneer species create soil.

7. New Soil
Soil begins to form as lichens and weather break down rocks into smaller pieces.
When the lichens die, they add organic matter to the rock.
Plants such as mosses and ferns grow in this new soil.

8. New Soil
The soil layer thickens, and grasses, wildflowers, and other plants take over.
When these plants die, they add more nutrients to the soil.
The soil can now support the growth of shrubs and trees and eventually animals.

9. Secondary Succession
After a forest fire, not much seems to be left except dead trees and ash-covered soil.
All that remains is bare soil.
But, the soil already
contains the seeds
of weeds, grasses,
and trees.
Causes: Fire, floods,
changes in climate, etc.

10. Climax Communities
A community of plants that has reached an end stage of succession.
There are fewer changes of species over time unless there is fire, etc.
This community is a relatively stable environment that can last for hundreds of years.

11. Succession Venn Diagram
Primary Succession
Secondary Succession
Both
Starts the ecosystem
Continues the ecosystem
Preexisting soil
No soil
At start – very few plants and animals
Started by a certain event (disaster, disease, etc.)
Starts on new land
Populations of species introduced to establish the ecosystem
Pioneer species start habitat

12. Succession Comparison Chart
Primary Succession
Secondary Succession
Begin with no life
Follows the removal of existing habitat
No soil present
Soil already present
New area (e.g. volcanic eruption)
Old area (e.g. following a brush fire)
Lichen and moss come first
Seeds and roots already present