succession

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Succession. Sequential change in the relative abundances of the dominant species in a community following a disturbanceDegradative succession: organic material degraded by detritivores and microorganismsAutotrophic succession: new community develops in empty habitat after disturbance. Autotrophic succession.

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1. Succession Chapter 13

2. Succession Sequential change in the relative abundances of the dominant species in a community following a disturbance Degradative succession: organic material degraded by detritivores and microorganisms Autotrophic succession: new community develops in empty habitat after disturbance

3. Autotrophic succession Primary succession: develops from abiotic situation after cataclysmic disturbance Secondary succession: develops from disturbed habitat, but not so severely that all life is destroyed (old field succession) Disturbance: event that disrupts ecosystems, communities, population structures; changes resource or substrate availability or abiotic environment (ex: storms, tornadoes, hurricanes, fires, volcanoes, mudslides, glaciations, etc…); disturbance is frequent!

4. Stages of succession Sequence of stages: sere Any one phase: seral stage Final stage: climax Climax persists and reproduces itself until next disturbance Under continuous disturbance, seral stage may be repeated: disclimax

5. Mechanisms of Succession Facilitation model: pioneering species modifies environment facilitating colonization by later species Tolerance model: colonizing species makes it difficult for offspring to survive; more tolerant species colonizes next Inhibition model: each species prevents further colonization during its lifespan; replaced by longer-living species

6. Mechanisms of Succession Tilman’s resource model: each species is competitively dominant for one limiting resource; as resources change, species composition changes Herbivores also play a role in succession by selective grazing As usual, mechanisms of successional changes are probably a mixture of all models

7. What determines Climax? Each area of a biome will reach a characteristic climax: monoclimax Local edaphic and microclimate variations lead to the polyclimax idea Climaxes grading into each other leads to the idea of pattern climax

8. Is a stable Climax viable? Climax implies equilibrium Does succession frequently lead to equilibrium? Data shows equilibrium is rare, and if attained, usually short-lived Most communities are usually at some stage of succession (often a disclimax)

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