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)