Download Systems approach

Systems Approach
Ecosystem
Community
Population
Landscape
Ecosystem
Community
-Populations of different species
that interact.
Ecosystem
- the various communities of organisms
interacting with the environment.
Landscape -a physical area such as a watershed
consisting of various landscape elements
(fields, forests) and the species found.
Community
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Species richness
Species diversity
Functional groups
Life Forms
Trend Analysis
Statistical Approach
Ecosystem
• Energy Flow
• Nutrient cycling
Landscape
• Spatial Arrangement of landscape elements
or units.
Community
• Central Question:
How is a community structured and by
what?
• Are there patterns in community structure?
• If so, what has caused this pattern
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Competition
Predation
Time
Size of patches (islands)
Equilibrium
Non-equilibrium
Equilibrium
- focus on the mean
Non-equilibrium
- focus on the variation
Equilibrium
Non-equilibrium
Mean
Predictability
Variation
Unpredictable
Competition
Island Biogeography
Succession
Disturbance
Competition
• An equilibrium concept.
Data from Gause 1934
• Competition is often not an important
structuring process in communities.
Species area relationship
• Preston (1948, 1960 and 1962)
– S = CAz
– log S = (log C) + z(log A)
Island Biogeography
• 2 processes - extinction and colonization
• Function of – island size and distance from
mainland.
Succession
Disturbance a non-equilibrium concept
-fire, insect damage, wind, flooding
-unpredictable in space and time
-results in non-equilibrium dynamics
-recognized as being central to ecosystems
Modeling Disturbance
Intermediate Disturbance Hypothesis
Predator Mediated Co-existence Hyp.
Effect of grazing on species richness
Succession
In the
Boreal Forest
Holling’s Four-Box Model of ecosystem function.
Keystone Species
Other Keystone species:
- Beaver (create ponds)
- Elephants (Trees)
- Sea otter (Seaurchins)
Community structure
• Equilibrium and non-equilibrium
AND
Time.
Complexity
Stability
Stability
Complexity
Complexity Stability Debate
• Elton Complexity -> Stability
• May 1970’s Modeling – Not so!
• Subsequently refuted (late 80’s & 90’s)
• Yodzis - modeling
– Tillman – experiments
– BUT we still did not understand the nature of
stability
• Populations
Summary
– movement
– Fragmentation
– Spatially structured populations
• Communities
– Dynamic equilibrium/non-equilibrium
– Competition
– Island Biogeography
• Protected areas - corridors
– Disturbance
• Intermediate disturbance hypothesis
• predator mediated co-existance
• Ecosystem stability