Large-scale Ecology Interacting ecosystems

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					Large-scale Ecology
 Interacting ecosystems
               Key terms
• Ecosystem- A specific biological
  community defined by the the composition
  of the community and the interacting
  physical environment.
• Landscape Ecology- The study of
  heterogeneous land area comprised of
  interacting patches of ecosystems.
     Landscape Ecology terms
• Patch- a geographic area that is relatively
  homogenous with respect to its surroundings
  (uniform habitat).
• Ecotype- A specific ecosystem/habitat patch.
• Matrix- most extensive ecotype present with in
  the landscape.
  – Patches are often said to be embedded within the
• Scale- the unit of measure
  of perception (spatial or
• The scale one observes a
  landscape at greatly
  influences the perception
  of the landscape.
• Different organisms
  perceive the ecosystem at
  different scales
Landscape ecologists study landscape structure and
     how that relates to functional processes.

• Structure focuses on aspects of the patches: their
  density, size, shape, orientation to each other,
  contrast between each other, etc. (overhead Fig 2)

• Landscape ecologist attempt to understand how
  neighboring ecosystems influence each other.
  Also address the impact of human landscapes on
  natural ecosystems.
          The Edge Effect:
• Ecotones- boundaries between different
  adjacent communities.
• Edge habitats often differ from both
  adjacent communities due to mixed species
  composition, temp., light, humidity, etc.
• Patch shape influences the amount of edge
  (Fig 4.21 text)

Increased light:-
Raises temperature
Increases air flow
Increases evaporation
             EDGES ARE DYNAMIC
                      Trees at the edge extend
                      their canopies and develop
                      epicormic branches

                                                   The gap
                                                   level and
   Shade intolerant plants
                                                   the canopy
   e.g. blackberries
                                                   is filled.
   become established in
   the new high light zone

This is an edge succession
           The Edge Effect:
• Edges show greater diversity than the
  communities that bound them.
• The degree of diversity is greatest when:
  – the adjoining communities are highly
    contrasting (forest - grassland),
  – the edge is long and wide,
  – patches are large enough to sustain the
    members of the original community.
      Fig. 15.10

•Habitat fragmentation our
environment is increasingly
becoming edge habitat. Our
most threatened organisms are
those that require core habitat.
Habitat Fragmentation –
    Cadiz Township, WI
              Edge effect
• Edges can often be more diverse, but at the
  same time can act as “traps” with greater
  risks of predation, parasitism, and or
• A large amount of preserved habitat doesn’t
  mean much if most of it is edge habitat. We
  must preserve large area with core habitat.
          Source-sink dynamics
• Metapopulations- set of spatially isolated
  subpopulations of a particular species living in
• Because of patch heterogeneity- some
  subpopulations are more productive than others.
   – some produce a surplus of individuals- sources
   – some produce insufficient offspring to sustain the
     subpopulation- sinks
   – Patch conditions vary between different species.
source-sink dynamics- source populations supply individuals
to sink population through emigration and immigration via




   Sink                                       Sink
                                        Fig. 15.11

* Harrison Ford and Conservation International
          Island Biogeography
Total species diversity of a isolated ecosystem
   (island) can be predicted based on: area, distance
   to nearest colonizing source, and extinction rate.
1. A larger area of land can sustain more species
   (More niche space)
2. Larger areas have lower local extinction rates
Diversity increases with land area:
             (See handout)
        Island Biogeography
3. Areas closer to source populations have a
   higher rate of colonization.
4. Areas with greater species diversity
   correspondingly have greater local
   extinction rates. Why?
5. Colonization rates decline as diversity
   increases. Why?
Equilibrium amount of species diversity is determined by the
          balance of these relationships (Fig 13.21 text):

                                                         Fig. 13.20
         Restoration Ecology
1. Replace a species- Endangered Species
2. Restore structure- species composition
   (but not function)
3. Restore function- water filtration, flood
   control, food web.
4. Restore all the above: synthesis
          Restoration Ecology
• Focus is usually specific- Population recovery or
  restoring habitat of endangered species. But
  increasingly efforts to restore large-scale
  ecosystems are underway- e.g. Florida Everglades.
• Complications: natural disturbance regimes (fire,
  floods, etc), alien species, pollution, resources
  (space), erosion, cost, public support, long-term
  maintenance and monitoring.
Fig. 5.21
Fig. 5.22
  Population Viability Analysis (PVA)-

modeling technique that incorporates life history,
  habitat requirements, metapopulation dynamics,
  species interactions, etc. to predict the probability
  of persistence of a population for a given time and
-     Minimum viable population- population size
  necessary for long-term persistence in an area.
-     Technique is used for restoration planning and
  for endangered species recovery plans.
       Adaptive management
• apply a management approach to restoration
  that experimentally evaluates the success of
  an ongoing project and modifies the
  strategy accordingly. Marries applied
  science with pure science.
Fig. 5.25

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