1. Endpoint? : Revisited Climax community “Relatively steady-state condition with no directional changes in species composition” Traditional view

2. Equilibrium View time Successional state “Climax”

3. time Successional state Equilibrium View? “Climax” Disturbance

4. Definition: “The interruption of tranquility, peace, rest, or a settled condition; interference with the due course of any action or process.

5. time Successional state Equilibrium View? “Climax” Disturbance

6. time Successional state Non-equilibrium View

7. Disturbance Definition: “The interruption of tranquility, peace, rest, or a settled condition; interference with the due course of any action or process. Disturbance is viewed as something disrupting natural events tending to equilibrium. Equlibrium view Disturbance is viewed as a natural component of a community, producing change over time. Small disturbances are always occurring, but do not necessarily lead to successional processes. Non-equlibrium view

8. Many Small Disturbances a study by Jane Lubchenko Coastal tidal pools

9. Elements in study Disturbance agent Litorina littorea Plant species (periwinkle snail) – density varies among pools – herbivore Chondrus crispus (Irish moss) – red alga – only eaten as last resort Eneteromorpha – green alga – relatively small – Tender and highly edible Numerous ephemeral algae species

10. Disturbance rate Disturbance Effects (herbivory) Disturbance rate Species richness Species diversity Low snail density Enteromorpha smothers Chondra Intermediate snail density Competitive exclusion reduced due to con- sumption of Entero- morpha by snails High snail density All but Chondrus eaten

11. Conclusion Disturbance is a constant influence that defines community structure

12. Intermediate Disturbance Hypothesis Michael Huston 1977

13. Two Species Succession High growth rate; poor competitor Low growth rate; good competitor Competitive exclusion

14. Impact of disturbance Disturbance removes 25% biomass Competitive exclusion halted or delayed

15. Potential Reversal of Fortunes

16. Multiple species extension Eventual winner

17. Multiple species extension Competitive exclusion is delayed Species diversity maintained at a higher level

18. Multiple species extension At high disturbance rates diversity declines again

19. Intermediate Disturbance Hypothesis Frequency of disturbance Diversity Highest diversity will be found at intermediate disturbance levels

20. A Field Test of the Intermediate Disturbance Hypothesis Wayne Sousa 1979

21. Study Location

22. Rocky Intertidal Plant Community

24. Boulder Size and Disturbance Small……….………………Large Newtons of pull = weight Low disturbance Medium disturbance High dist.

25. Diversity and Disturbance High MediumLow Disturbance rates Maximum diversity

26. Predicting Species Distributions mid-successional species

27. Mid-succession species and disturbance Distribution as predicted

28. Assessing impact of disturbance Early succession Mid-succession Late succession

29. Conclusion Results of this experiment are consistent with the intermediate disturbance hypothesis

30. Further studies examining diversity-disturbance relationships Mackey and Currie 2001

31. Meta-analysis pattern predicted by intermediate disturbance hypothesis Disturbance response

32. Conclusion The intermediate disturbance hypothesis is only one of many possible relationships observed between diversity and disturbance

33. Ecology at the Global Scale

34. Global Climate Change: Impacts on Vegetation

35. Part #1: The Driving Force behind Climate Change

36. The Greenhouse Effect CO 2 (Carbon dioxide) NH 4 (Methane) N 2 0 (Nitrous oxide) O 3 (Ozone) CFCs

37. Mauna Loa: CO 2 Measurements 4,170 m

38. Mauna Loa: [CO 2 ] Summer minimum Winter maximum Mean trend

39. Does this represent a long term trend?

40. Fossil AtmospheresMauna Loa Further Evidence