Download Community Community Development

22 Community Development
Outline
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Concepts & definitions
Primary & Secondary Succession
Patterns & Mechanisms
Species involved
Applications
Community
Community Development
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• Why do communities change?
• Why do communities stay the same?
• What aspects of communities change?
Fig. 21.4
Structure
Function
Time
– Snapshot
– Progression
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Perturb
Disturb
• Fig. 21.10
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Succession
Sere
• Ricklefs
• Replacement of populations in a habitat
through a regular progression to a stable
state.
• Ricklefs
• A series of stages of community change
leading toward a stable state.
• Different seres can lead to same endpoint.
Many species
Fire
Flood
Dune blowout
Ice scour
-> Recovery to stability
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Climax community
Seres
• Ricklefs
• The endpoint of a successional sequence
or sere; a community that has reached a
steady state under a particular set of
environmental conditions.
• Multiple paths
to same climax
community
Bush 2000
Primary Succession
Primary Succession
• Ricklefs
• The sequence of communities developing
in a new habitat devoid of life.
• Figures 22.1, 22.2
• Krakatau 1883
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Primary Succession
Primary Succession
• Bog succession
• Bog succession; Fig. 22.6
Secondary Succession
Primary & Secondary Succession
• Less sever disturbance
• Return to climax community
• Faster
• Some gradation
– Intensity vs. size
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Primary Succession
Species Replacement?
• Why? - No purpose
• Adaptations to habitats
• Mechanisms
– Facilitation
– Interference
– Tolerance
Bush 2000
Facilitation
Facilitation
• Given habitat - few species can invade
• Invaders alter microhabitat
• Alder - N-fixing symbiotic bacteria
Molles 2002
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Facilitation
Facilitation
• Surfgrass
• Surfgrass - Fig 22.11
www.marine.gov/phyllospadix.htm
Facilitation
Inhibition
• Surfgrass - Teresa Turner
• Species prevent colonization by others
– Predation, competition
Molles 2002
courses.uvi.edu/mbi/
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Inhibition
Inhibition
• Sousa - Fig. 22.8
• Limpets & algae - predation
• Sousa - algal competition
Molles 2002
Tolerance
• Tolerates physical conditions
– Few biological interactions
• Early colonizer species
Succession - Temporal Patterns
• Initial stages - rapid
turnover of species
• Later stages - slow turnover
• Fig. 22.12
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Succession - Temporal Patterns
Succession - Temporal Patterns
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• Western grasslands - 20 - 40 yrs. secondary
• (soil chemistry ~100 yrs.)
150yrs - secondary
1,000yrs - primary
Bush 2000
Succession - Temporal Patterns
Climax community
• Glacier Bay Alaska
• Limits set by climate - temperature, rain, energy
Time
Molles 2002
Molles 2002
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Climax community
Climax community
• Limits set by climate - sun, rain, energy
• Biomass and productivity in aquatic system
• Progression towards:
– Higher biomass
– More nutrients in biomass
Molles 2002
Climax community
Structure vs. Composition
• Characterized by:
• Negligible species turnover
• Structure - increasing complexity
• Species - may still change somewhat
• Fig. 22.14
– Cannot be invaded
– Analogous to ESS concept
Bush 2000
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Diversity
Climax - Reality
• Most diverse at intermediate stages of succession
• Not total dominance by a few species
• Heterogeneity
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– disturbance
Clements - 14 terrestrial climax communities (NA)
Recent research - subtle differences
Fig. 22.9
Local conditions
Smith & Smith 2001
External Influences
Species Characteristics
• Lodgepole Pine and fire
• Prairie-forest edge
• Colonizers vs. competitors - Table 22.1
– fire and bison grazing
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Species Characteristics
Species Characteristics
• Life history features - Table 22.2
• Life history features - Fig. 22.15
Colonizer
Competitor
Species Characteristics
Animals!
• Survivorship
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Molles 2002
Molles 2002
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Animals!
Resource Exploitation
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• (Fisheries)
• Forestry
– Clearcut
– Selective
Smith & Smith 2001
Bush 2000
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