Ecological succession is the gradual replacement of one community by another over time. It is initiated by disturbances that remove existing organisms or alter resources and habitat. There are two types of succession: primary succession occurs in areas without soil, while secondary succession occurs in areas with existing soil following a disturbance. In both cases, pioneer species are the first to colonize, and succession progresses gradually until an equilibrium climax community dominated by less tolerant species is reached if undisturbed.

1. Ecological Succession

2. Stability vs Change
• Stability = the tendency
of a community to
maintain relatively
constant conditions.
• More stable
communities = better
able to resist changes
• Disturbances = events
that change
communities
• Can be abiotic or biotic
– Remove or destroy
organisms
– Alter resource
availability
– Habitat destruction

3. Community Change
Ecological succession - gradual
replacement of one kind of community
of organisms by another over time
Initiated by disturbance

4. Ecological Succession: Communities in
Transition - Type #1
Primary succession
- begins with barren area, no soil

5. Ecological Succession: Communities in
Transition - Type #1
Slow soil development by weathering,
activities of tolerant species
- pioneer species

6. Ecological Succession: Communities in
Transition - Type #1
Gradual changeover to less tolerant
species over long periods of time
- equilibrium or successional species

7. Primary Succession

8. Ecological Succession: Communities in
Transition - Type #2
Secondary succession
- begins with soil already in place

9. Ecological Succession: Communities in
Transition - Type #2
Rapid changeover to less tolerant
species over shorter periods of time
- rapid because soil already present

10. Secondary Succession

11. Succession and Wildlife

12. The End Product
If undisturbed, communities change
toward a relatively stable stage
- climax community
- long-term presence if not disturbed
- dominated by less-tolerant species
- general equilibrium

13. SUCCESSION SUMMARY
Succession: the gradual regrowth of species in an area
2 Types:
 1) Primary Succession: in an area that has not previously
supported life
 2) Secondary Succession: follows a disruption of an existing
community
 i.e. flood, fire, etc.
Pioneer Species: the first species to colonize a new habitat
Climax Community: the end result of succession which
remains constant over time
-The “Biome”