1. Changes in Ecosystems: Ecological Succession

2. Definition:
Natural, gradual changes in the types of species that live in an area; can be primary or secondary
The gradual replacement of one plant community by another through natural processes over time

3. Primary Succession Begins in a place without any soil
Sides of volcanoes
Landslides
Glaciers receding
Starts with the arrival of living things such as lichens that do not need soil to survive
Called PIONEER SPECIES

4. Lichens!

5. Pioneer Traits
Generalist- can thrive in a wide range of environments and habitats
Temperatures, Precipitation, pH
Reproduce quickly and often- spread fast
The plants we call “weeds” are pioneers
We try to kill them, but keep coming back

6. Primary Succession
Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces
When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil
As soil begins to form, more organisms colonize the area.

7. Next Generation after Lichens – Mosses, small plants (ferns)

8. Primary Succession
Simple plants like mosses and ferns can grow in the new soil

9. Primary Succession
The simple plants die, adding more organic material to the new soil
The soil layer thickens, and grasses, wildflowers, and other plants begin to take over

10. Primary Succession
These plants die, and they add more nutrients to the soil
Soil can now support shrubs and trees

11. Primary Succession
Insects, small birds, and mammals have begun to move in
What was once bare rock now supports a variety of life
Takes a LONG
Time= yrs

13. Secondary Succession
Location that has soil but underwent a DISTURBANCE such as
Forest fire
Flood
Human Change- farms, housing, deforestation
Occurs faster and has different pioneer species than primary succession

16. Nature will return
Evidence of succession is observable in rural, suburban, or urban settings
Humans attempt to stop/hinder succession

18. Climax Community
A stable group of plants and animals that is the end result of the succession process
The “textbook” ecosystem for that biome
Does not always mean big trees
Grasses in prairies
Cacti in deserts

19. Aquatic Succession
Succession also occurs in aquatic ecosystems, especially lakes and ponds
Primary: Lakes fill in for the first time
Ex: glacier retreats and melts, creating lake
Secondary: Over time, lakes and ponds fill with runoff / sediment and decaying organisms

20. TIME

21. Eutrophication
Occurs when excessive nutrients enter an aquatic ecosystem and stimulate rapid producer growth
Natural process, but humans ACCELERATE.
Excessive fertilizers (N and P) used on lawns, golf courses, farm fields that runoff into local waterways.

22. Eutrophication Excess Nitrogen and Phosphorus enter lake.
Algae LOVE N&P- algae reproduces fast and furiously, called “algae bloom”
As algae take over, they die and sink, decomposers use up oxygen to break down.
Algae mats on surface also block sunlight, killing more organisms, and giving decomposers more to eat.
Over time, water body becomes hypoxic, or starved of oxygen, thus dead and unusable to life
Hypoxic zones harbor bacteria that emit dihydrogen sulfide (rotten-egg gas), a poison for other life. These areas are sometimes called dead zones.

23. Examples

26. Summary Primary vs. Secondary Succession
Change is a certainty in life, even in climax communities
Nature bounces back from disturbances, but it takes a long time
Humans try to prevent succession on land, but promote it indirectly in lakes through eutrophication.