BIOL1007 Lecture Notes - Lecture 23: Secondary Succession, Primary Succession, Move
19 May 2018
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Groups of species that live together and interact with each other as an ecological unit
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Often taken to be just vegetation but should include ALL biota that occur together
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Gradual transitions more common rather than abrupt hard edges e.g. terrestrial-
marine transition
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Ecotones are usually a transitional are between 2 different communities e.g.
woodland and heath
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Ecotones - where does one community start/finish?
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Change in composition is constant in nature
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Local colonisations and extinctions
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Classic models driven by succession
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Predictable pattern of change in response to a disturbance
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Over time they…
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Communities: Species that occur together in space and time
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e.g. plant communities
Screen clipping taken: 23/10/2017 9:07 AM
Assemblages: less well defined, a group of species that live together with no assumptions
made about how or whether they interact with each other
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Communities as a definable entity
Primary succession - bare are without soil, invasion of previously unoccupied area e.g.
sand-dune and bare rock
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Secondary succession - in a habitat modified by other species e.g. forest gaps,
abandoned agricultural fields
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Types of succession
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e.g. tree falls down in forest -> light gap -> light unsuitable for some species and very suitable
for others -> change in species composition and abundance, growth rates in lower canopy
stratum -> dominant species in system change overtime -> NEW DOMINANTS MOVE IN
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Succession
L23 - Assemblages and ecosystems
Monday, 23 October 2017
9:03 AM
mod 4 - ecology and ecosystems Page 1
Screen clipping taken: 23/10/2017 9:15 AM
Facilitation - initial species make environment more favourable for later species
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Tolerance - neither negative nor positive interactions between early and late species,
just a matter of time
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Inhibition - early species inhibit later species
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Models of succession
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Screen clipping taken: 23/10/2017 9:17 AM
Grow in sun
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Fix nitrogen
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Good dispersal
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Small seeds
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Rapid growth
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Short generation time
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Pioneer species
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Shade tolerant
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Slow growth
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Good competitors
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Long-lived
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Climax species
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Plant species' role in succession
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Self-perpetuating, no replacement
Climax community - final community in a successional series
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mod 4 - ecology and ecosystems Page 2
Document Summary
Communities: species that occur together in space and time. Groups of species that live together and interact with each other as an ecological unit. Often taken to be just vegetation but should include all biota that occur together. Gradual transitions more common rather than abrupt hard edges e. g. terrestrial- marine transition. Ecotones are usually a transitional are between 2 different communities e. g. woodland and heath. Predictable pattern of change in response to a disturbance e. g. plant communities. Assemblages: less well defined, a group of species that live together with no assumptions made about how or whether they interact with each other. Primary succession - bare are without soil, invasion of previously unoccupied area e. g. sand-dune and bare rock. Facilitation - initial species make environment more favourable for later species. Tolerance - neither negative nor positive interactions between early and late species, just a matter of time. Climax community - final community in a successional series.
