Succession and Stability

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Chapter 20

• Succession and Stability

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Succession

• The gradual change in plant and animal
  communities following disturbance or the creation
  of new substrate

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Community Change
During primary succession a community that starts
with no loving materials quickly adds
species Species addition also occurs in
secondary succession, where a community begins
with some living material
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Community Change
As the number of species increases the
physiognomic characteristics of the community
change as well.
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Community Change
Intertidal areas exhibit similar patterns during
succession to the ones we saw in terrestrial
ecosystems
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Community Change
We also see species richness increase during
succession in streams
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Ecosystem Change
Properties of ecosystems change during
succession. One important property is soil
development
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Ecosystem Change
Soil Moisture
Nitrogen Conc.
Organic Content
More Soil Development
Phosphorus Conc.
pH
Bulk Density
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Ecosystem Change
Hubbard Brook deforestation experiments
Biomass
Calcium
Annual Export
Potassium
Nitrate
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Ecosystem Change
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Facilitation
Tolerance
Inhibition
Successional Mechanisms
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Mechanisms Glacier Bay Spruce
Inhibition and Facilitation were observed at
Glacier Bay
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Stability

• The absence of change
• Resistance the ability to maintain structure
• Resilience the ability to recover from
  disturbance

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Community Stability
No Fertilizer
Where a community stabilizes is related to the
environmental conditions of the site
legumes
P, K, Na
grasses
N, P, K, Na, Mg
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Species Instability
While the community may remain stable, population
sizes of individual species can change
dramatically
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Resilience
The availability of resources, such as nutrients,
can influence the ability of the ecosystem to
recover from disturbance (resiliency)
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Summary

• Community changes during succession
• Ecosystem changes during succession
• Facilitation, Tolerance, and Inhibition
• Stability resistance and resilience