1. Changes in Ecosystems: Ecological Succession Pete HamiltonSandringham College

2. Succession: The gradual replacement of one plant/ animal community by another through natural processes over time.

3. Autotrophic succession is characterised by early and continued dominance of autotrophic organisms. It begins in a predominantly inorganic environments and the energy flow is maintained indefinitely. This is gradual increase in the organic matter content supported by energy flow.

4. Heterotrophic Succession: is characterised by early dominance of heterotrophic organisms such as bacteria, fungi, moulds and animals. It begins in a medium which is rich in organic matter such as rivers, streams, which are polluted heavily with sewage or in small pools receiving leaf litter in large quantities.

5. Allogenic succession Serial replacement of species driven by changing external geophysical processes. Factors external to the plants cause succession (climate change, fires,floods) Example: silt deposition changing an aquatic habitat to terrestrial habitat

6. Autogenic succession Change of species driven by biological processes changing conditions and/or resources The plants themselves cause succession to occur ( light capture, production of detritus, water and nutrient uptake, nitrogen fixation) Example: organisms living, then dying, on bare rock

7. Primary Succession: is the series of community changes which occur on an entirely new habitat which has never been colonized before.

8. Primary Succession Krakatoa : A Case Study in Primary Succession

12. Primary Succession Begins in a place without any soil –Sides of volcanoes –Landslides –Flooding Starts with the arrival of living things such as lichens that do not need soil to survive Called PIONEER SPECIES

13. Pioneer species: initiate recovery following disturbance in both primary AND secondary successions Pioneers "pave the way" for later colonists by altering the biotic and abiotic environment: –soil stabilization –soil nutrient enrichment –increased moisture holding capacity –light availability –temperature –exposure to wind

14. http://botit.botany.wisc.edu http://www.saguaro-juniper.com/ Lichens: Every lichen species is composed of two, possibly three, distinct species of organisms. a kind of fungus. an alga, sometimes a photosynthesizing bacterium cyanobacterium.

15. Primary Succession Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces When lichens die, they decompose, adding small amounts of organic matter to the fragmented rock to make soil.

16. http://www.life.uiuc.edu

17. Primary Succession Simple plants like mosses and ferns can grow in the new soil http://uisstc.georgetow n.edu http://www.uncw.edu

18. Primary Succession The simple plants die, adding more organic material to the soil. The soil layer thickens, and grasses, wildflowers, and other plants begin to take over http://www.cwrl.utexas.edu

19. Primary Succession These plants die, adding more nutrients to the soil Shrubs and trees can survive now http://www.rowan.edu

20. Primary Succession Insects, small birds, reptiles and mammals move in. What was once bare rock now supports a variety of life

21. Secondary Succession: is the series of community changes which take place on a previously colonized, but disturbed or damaged habitat.

22. Secondary Succession Begins in a place that already has soil and was once the home of living organisms Occurs faster and has different pioneer species than primary succession Examples: –After forest fires – Hurricanes – Floods

23. Primary - slow - may take 1000s of years Secondary - faster - fraction of the time to reach same stage Rates of Succession

24. http://www.geo.arizona.edu

25. http://www.ux1.eiu.edu

26. Climax Community Communities become stabilized Reaches equilibrium Little or no change in species composition, abundance over long periods of time End stage of succession Does not always mean big trees –Grasses in prairies –Cacti in deserts

27. summary of changes that occur during succession: Pioneer species colonize first. Pioneer species alter the environmental conditions remaining after the disturbance. Eventually new species of plants become established in the conditions altered by the pioneer species and displace the pioneer plants. Animals come in with or after the plants they need to survive. Further environmental change by the new plants and animals result in the establishment of different species. With infrequent disturbance, a stable climax community consisting of plants and animals that can reproduce themselves in the existing conditions will become established. Disturbance of the ecosystem will start the process of succession anew. In a given area there are usually small patches of land in different stages of succession, depending on the time and severity of the last disturbance. This adds diversity in the types of vegetation and animals living in the greater region.