1. Community Ecology Chapter 9

2. Succession Temporal patterns in communities Replacement of species by others within particular habitat (colonization and extinction) Non-seasonal, continuous, directional

3. Degradative succession Decomposers breaking down organic matter Leads to disappearance of everything, species included

4. Autotropic succession Does not lead to degradation Habitat continually occupied by living organisms

5. Two types of autotropic succession Allogenic succession Autogenic succession

6. Allogenic succession Serial replacement of species driven by changing external geophysical processes Examples: 1) silt deposition changing aquatic habitat to terrestrial habitat 2) increasing salinity of Great Salt Lake

7. Autogenic succession Change of species driven by biological processes changing conditions and/or resources Example: organisms living, then dying, on bare rock

8. Autogenic succession can occur under 2 different conditions In an area that previously did not support any community Primary succession Example: terrestrial habitat devoid of soil In an area that previously supported a community, but now does not Secondary succession Example: terrestrial habitat where vegetation was destroyed, but soil remained

9. Primary succession Volcanic eruptions Glaciers

10. Secondary succession Floods Fires

11. Rate of succession Primary - slow - may take 1000s of years Secondary - faster - fraction of the time to reach same stage

12. Autogenic succession begins… First community comprised of r-selected species - pioneer species

13. r-selected species Good colonizers Tolerant of harsh conditions Reproduce quickly in unpredictable environs Example: lichens

14. Pioneer species Carry out life processes and begin to modify habitat Extract resources from bare rock Break up/fragment rock with roots Collect wind-blown dust, particles Waste products accumulate Die and decompose Soil development begins

15. Continuing change Colonizers joined by other species suited for modified habitat Eventually replace colonizers Better competitors in modified habitat Less r-selected, more K-selected

16. More change Communities gradually become dominated by K-selected species Good competitors, able to coexist with others for long periods of time

17. Stability Communities become stabilized Reach equilibrium Little or no change in species composition, abundance over long periods of time Climax community End stage of succession

18. Will climax stage be reached? Rarely is climax stage reached quickly Slow succession most common, climax stage almost never achieved Community usually affected by some major disturbance (e.g., fire) before climax stage is reached Resets succession, forces it to start again from some earlier stage

19. Terrestrial succession

20. Lake or pond succession