Download Succession - Renton School District

Succession
11/3
Succession
Succession- the increase in complexity of the
structure and species composition of a
community over time.
When you have a blank ecosystem what species
come colonize first, second, third and finally
balance out the system.
Succession
• Succession happens in steps called seral
stages.
Primary Succession
Primary Succession- colonization of newly
created land.
Examples:
• volcanic eruptions
• sand dunes
• uncovered glacial deposits
Primary Succession
1st things to colonize an area are called
pioneer species.
1. Colonization
No soil at the beginning of primary succession.
Colonizers: Lichen, mosses (r-selected)
- Drought resistant and help break down rock to
create soil.
- When they die they create organic material.
Primary Succession
2. Establishment
As the soil builds water can be held better and
shallow roots can establish. As these plants
die, organic material is added
Establishing species: grasses, small plants, small
invertebrates that break down plant matter.
Primary Succession
3. Competition
Weathering and rock breakdown create enough
soil for K-selected species.
K- selected species start to push out r-selected
colonizers.
Competition species: shrubs, shade-intolerant
plants, pine trees.
Primary Succession
4. Stabilization
• Soil in now fully established and nutrient rich.
This allows for deep roots and water
retention.
• Fewer new species are coming in.
• Slower growing, less productive, longer life
cycles
Stabilization species: (K-selected) shade tolerant
trees, oak, spruce, Douglas fir, maple
Primary Succession
Climax Community –Maximum possible
development a community can reach.
• Stable, self perpetuating.
• Equilibrium, organisms die at the same rate
they grow. Biomass is stable.
• Biodiversity is high, K- selected species with
specific niches are present.
Secondary Succession
Secondary succession- colonization of already
established land.
• Occurs on already established soil.
• Seeds can lay dormant
• Shortened/ Faster seral stages
Examples:
• Fire
• Flood
• Human activity (clear cutting) (agriculture)
• Natural disaster
Disturbance
• Disturbance can send the community back to
a previous stage
Changes that occur during succession
•
•
•
•
•
•
Size of organisms increases
Food webs become more complex
Soil depth increases
Biodiversity increases
NPP and GPP rise and then fall
Production/Respiration ratio falls
Why do these changes occur???