1. 4.3 Succession *Need book- Pg. 106
September 24th, 2013
4.3 Succession
*Need book- Pg. 106

2. How do natural disasters,
like volcanoes,
hurricanes, or fires,
affect ecosystems?

3. Ecological succession
A series of more-or-less predictable changes that occur in a community over time
Ecosystems change over time, especially after disturbances, as some species die out and new species move in

4. 2 Types: 1.Primary succession
Occurs on bare rock where no soil exists
No remnants of older communities
Ex: Volcanic eruption – covers ground with ash, rock, and lava (Mt. St. Helens, WA)
Ex: Retreating glaciers expose barren rock (Glacier Bay, Alaska)

6. How does life start to grow?
*Pioneer species – the first species
to populate an area
Ex: Lichen – organism formed by mutualistic relationship of fungi and algae
Able to grow on bare rock
Over time, break down rock and form soil
Nitrogen fixating!

7. Pioneer species – 1st to grow
Ferns
Lichen

8. 2. Secondary succession
Occurs where disturbance affects the community, but does not completely destroy it
Proceeds faster than primary succession because soil exists already
Ex: Wildfire, hurricanes, logging, farming

9. Secondary succession

10. Compare Fig and 4-13 p
Can you tell which one illustrates primary succession and which illustrates secondary?
Notice the amount of time it takes for the full community to recover in primary versus secondary succession

11. Do ecosystems return to “normal” after a disturbance?
Secondary succession in healthy ecosystems following natural disturbances often creates the original climax community
Climax community – the end result of ecological succession
Ecosystems may not recover from extensive human-caused disturbances (Ex: clearing of rain forests)

12. Mt. St. Helens, WA Erupted May 18th, 1980
Eruption was caused by 5.2 magnitude earthquake, which triggered a massive landslide
Released built up pressure, emitted volcanic ash 16 miles high!
US Congress acted quickly to protect land so scientists could study ecological succession in the “unique, living laboratory” the volcano created

13. Ash distribution across US

14. Videos
(Mt. St. Helens 1.22)
(30 yrs later 3.50)
(Primary succession 1:21)
(Song 4.00)