Disturbance and Succession

• Community properties• Dynamics• Succession• Species composition

& Distribution

Community

• What is a community?• Chance assemblage

of species?• Individualistic

hypothesis• Interactive hypothesis• Continuous vs

discrete boundaries

Dynamics

Community Dynamics

• Changes over time• Change in species #• Change in species

composition

Succession: Primary

• Occurs after major geologic event

• Glacier• New volcanic island• From bare rock, very

little soil

Species Dispersal

Succession: Primary

Succession: Secondary

• Existing communities have been cleared• Soil present• Volcanic explosion• Farming• Fire

Disturbance

Oak- Hickory Forest

Species composition & Distribution

• Species richness# of species

• Species abundance# present in each

species• Biodiversity

Diversity and Evenness Indices

Sample Calculations

Example

Community structure

Transition matrix

Summary

• What is a community?• Does it reach climax community• Disturbance effects• Species composition/number• Diversity index