Intermediate level of disturbance hypothesis (idh)

Intermediate Disturbance Hypothesis (IDH)

1. Intermediate Disturbance Hypothesis (IDH) Ariane Ruby B. Sogo-an Advanced Ecology

2. Learning Objectives: Explain the link between Biodiversity and Stability. Determine the disturbance factors that contributes to the variation of species in a given area. Explain the Intermediate Level of Disturbance.

3. “Are diverse communities more stable than species- depauperate communities?” “Are stable systems more diverse than unstable system ?”

4. Factors that affects species diversity: Invasive Species Keystone Species Availability of Resources 4. Stability of Community “How do say that an environment is stable or disturbed ?”

5. What is disturbance in the aspect of Ecology? Is a temporary change in average environmental conditions that causes a pronounced change in an ecosystem. Disturbances often act quickly and with great effect, sometimes resulting in the removal of large amounts of biomass. 

6. “Are diverse communities more stable than species- depauperate communities?” “Are stable systems more diverse than unstable system?”

7. Intermediate Level of Disturbance Hypothesis (IDH) Joe Connel (1978), the highest local diversities are actually maintained NOT in stable systems but in communities of levels of disturbance.

8. High level of Disturbance: Only good colonists (r-selected species) will survive giving rise to low diversity. Low Level of Disturbance: Competitively dominant species will out compete all other species and only a few k-selected species will persist, yielding low diversity. Most Diverse lies in between. Hence, Intermediate.

9. Examples of communities with High species diversity: Rain Forest (diversity maintained by storms) Coral Reefs (Diversity maintained by Hurricanes)

10. Seth Reice (1994) Disturbance operates in habitats of all types and naturally disturbed areas are nearly always more diverse than undisturbed areas. Many communities exist in nonequilibrium state in which the species composition changes.

11. Wayne Sousa (1979) Small boulder – 1.7 sessile plants/animal sp. Large Boulder – 2.5 sp. Intermediate Boulder – 3.7 mean sp k and r sel. ~Rock Stability vs. Rock Size

12. Summary The most diverse communities are not necessarily the stable. Rather, the most diverse communities seem to exist at intermediate level of disturbance.

13. End of report