1. Community Ecology Part 2
AP Biology
Community Ecology
Part 2

2. Disturbance and harmful effects
With Pisaster (control) 20 15
Number of species
present
Without Pisaster (experimental) 10 5
1963
’64
’65
’66
’67
’68
’69
’70
’71
’72
’73

3. Disturbance (Beaver Dams)

4. Fire and Disturbance Before a controlled burn.
A prairie that has not burned for several years has a high propor-tion of detritus (dead grass).
During the burn. The detritus serves as fuel for fires.
After the burn. Approximately one month after the controlled burn, virtually all of the biomass in this prairie is living.

5. Stages of Succession Pioneer stage, with fireweed dominant Dryas stage60 50 40
Soil nitrogen (g/m2) 30 20 10
Pioneer
Dryas
Alder
Spruce
Successional stage
Spruce
stage
Nitrogen fixation by Dryas and alder
increases the soil nitrogen content.

6. Succession (Mount St. Helens, WA)

7. Primary Succession (Remember Hawaii?)

8. Primary Succession (Pioneer species)

9. Primary Succession

10. Primary succession

11. Primary Succession Climax Community (Hawaii today)

12. Secondary succession (Forest fire destroys the forest)

13. Secondary Succession (Then over time…life returns)

14. Richness vs. Abundance

15. Richness and land area size

16. Richness and Land area

17. Equitorial Gradients and Species

18. E.O Wilson A Native Alabamian

19. Richness and Islands

20. Pygmy Elephant of Indonesian Islands