1. Ecological Succession: How Change Occurs in an Ecosystem

2. Ecological Succession: Replacement of One Community with Another
Ecosystems change over time
May be stable for a long time before an event occurs to change them
Fire, logging, agriculture etc.
Stable community may grow back but may be different
Some species die out; some move in
Typically, the number of species increase

3. Ecological Succession
Can be primary or secondary
Gradual replacement of one species with another
First species makes environment more hospitable for the next

4. Climax Community
A stable group of plants and animals that is the end result of the succession process
Does not always mean big trees
Grasses in prairies
Cacti in deserts
Succession may follow different paths ending up with different climax communities

5. Primary Succession
Begins in an area with no remnants of an older population
Lava
Bare rock succession
PIONEER SPECIES: First species to colonize the area
Lichen: symbiosis between alga and fungus.
Produce acids that help weather rock
Trap wind-blown soil particles
Followed by Moss: Trap more soil and create moister environment

7. Primary Succession
Once lichens create soil, less hospitable for themselves, more hospitable for other species.

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

9. Primary Succession The simple plants die, adding more organic material
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
Shrubs and trees can survive now.

11. Primary Succession

12. Secondary Succession Annuals to perennials to shrubs to trees
Occurs after a disturbance
Examples: Fire, Hurricane, Logging, Farming
Begins in a place that already has soil and was once the home of living organisms
May be some seeds remaining
Occurs faster than primary succession
Annuals to perennials to shrubs to trees

14. Succession after a Natural Disturbance
Healthy ecosystems can recover from disturbances and often reproduce original climax community
Frequent disturbances mean less stable climax community

15. Succession after Disturbances by Humans
Ecosystems may or may not recover from extensive human-caused disturbances
May change the microclimate and soil sufficiently to prevent re-growth of original climax community.

16. Succession in pond environments
Lake slowly filled in by organic and inorganic sediments
Living things decay
Streams bring in inorganic sediments
Bog to meadow