Lecture 34: Disturbance Ecology

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Lecture 34 Disturbance Ecology  

• By the end of this lecture you should be able to
• Define different types of ecological disturbance
• Concepts and terms physical, biological,
  anthropogenic disturbance
• Discuss the ecological significance of studying
  disturbance
• Concepts and terms equilibrium versus
  non-equilibrium forces
• Discuss some of the large-scale disturbances in
  the earth system caused by human activities.
• Concepts and terms alteration of nitrogen
  cycle, acidic rain, atmospheric CO2 enrichment

• Discuss fire as an important natural process
• Concepts and terms fire frequency, fire
  suppression, nutrient regeneration, natural
  habitats
• Discuss how ecologists study fire history
• Concepts and terms charcoal particles
• Discuss climate-fire-vegetation interaction.
• Concepts and terms autecology, fuel load
• Assigned reading Chapter 53, pages 1171-1175
  Chapter 54, pages 1200-1206 Campbell and Reece.

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• Disturbances are events like fire, weather, or
  human activities that can alter communities.
• Some are routine.

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• Marine communities are subject to disturbance by
  tropical storms.

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Anthropogenic disturbance
Karr, 1985
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Equilibrium vs. Nonequilibrium Forces
Influencing Community Structure
Equilibrium stability, climax community -Competi
tion -Predation -Other species
interactions Nonequilibrium communities
constantly changing -Disturbances -Recruitment
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• Highest species diversity is found at
  intermediate level of disturbance
• High disturbance leads to death of species
• Low disturbance limits species through dominance
  and competition

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Humans are the most widespread agents of
disturbance

• Human activities cause more disturbance than
  natural events and usually reduce species
  diversity in communities.

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• In agricultural ecosystems, a large amount of
  nutrients are removed from the area in the crop
  biomass.
• After awhile, the natural store of nutrients can
  become exhausted.

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Combustion of fossil fuels is the main cause of
acid precipitation
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http//www.nps.gov/yell/nature/fire/
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Andrea Hui Former IB150 student James Scholar
Current MD student at UIC
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1 Hypotheses Ho Forest fire occurs more
frequently when climate is warmer and
drier. H1 Forest fire does not occur more
frequently when climate is warmer and drier.
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2. Research methods
Paleoecology

• Charcoal, pollen

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3. Results
Macroscopic charcoal (gt180 ?m)
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autecology
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• 4 Conclusion
• Ecological traits of dominant species are
• as important as or more important than climate
• for fire occurrence.
• 5 Questions (critical thinking)!!
• Is this conclusion applicable to plant
  communities
• in other regions?
• Is it applicable to future conditions?