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					  Introduction – Landscape Ecology
• Landscape Ecology: Study of landscape
  structure and processes.
  – Landscape: Heterogeneous area composed of
    several ecosystems.
  – Landscape Elements: Visually distinctive
    patches in an ecosystem.
 Vancouver Island marmot
(Marmota vancouverensis)
                   ~100 left




              Isolated from hoary and
                 Olympic marmots
 Vancouver Island marmot
(Marmota vancouverensis)




     Natural tree succession
 Vancouver Island marmot
(Marmota vancouverensis)


               • Logging – disjunct patches
                   - max. dispersal = 7 km
               • Climate
               • Prey-Predator Dynamics
Human Land Use Practices

1) Agriculture
2) Suburban Development

Let’s pick on Indiana:

•   97% of land in state = privately-
    owned
•   In central Indiana,
    • 70+% of land in row crop
    • <10% in forest
    • Urban sprawl intensifying
        Human Impacts
Ecosystem simplification: elimination of
  species from food webs via human
  alterations to land
Example: vertebrate communities in ag.
  landscapes
Intensive Agriculture
         &
   Clean Farming
Timber Extraction
       &
  Fragmentation
   Formation of
Terrestrial “Islands”
     Habitat Fragmentation
• Process of breaking contiguous unit into
  smaller pieces; area & distance
  components
• Leads to:
     < remnant patch size
     > edge:interior ratios
     > patch isolation
     < connectivity
• Community & Ecosystem processes
  altered
   Formation of
Terrestrial “Islands”
Habitat Loss vs. Habitat Fragmentation
  #patches        Patch size




Patch isolation
                   Edge
  What about
aquatic systems?
  What about
aquatic systems?
 Con.Bio 12(6)
     Habitat Fragmentation
 • area-sensitive species: species that
   require minimum patch size for daily
   life requirements
• Edge effects: influence of factors from
   outside of a patch
Increased Edge Habitat
Increased Edge Habitat
           Edge Effects
• Habitat surrounding a patch can:
  - change abiotic conditions; e.g., temp.
  - change biotic interactions, e.g.,
    predation
Example of nest predation = edge effect of
  approximately 50 m into forest patch
     Habitat Fragmentation
• First-Order Effects: fragmentation leads
  to change in a species’ abundance and/or
  distribution
     Habitat Fragmentation
• Higher-Order Effects: fragmentation
  indirectly leads to change in a species
  abundance and/or distribution via altered
  species interactions
                     HABITAT FRAGMENTATION


                                                         Predators
                                                  - Abundance
                                                + - Distribution
                              Ground-
                                                  - Foraging Behaviors
                            Nesting Birds
                           - Abundance      –
                         – - Distribution                      –
Avian Competitors
                     +                                              +
   Avian Prey
 Brood Parasites                                               Parasites
                                                            - Abundance
                                                            - Distribution


                    REPRODUCTIVE SUCCESS
Habitat Fragmentation: Species-
     Specific Sensitivity?
• Rare species = more vulnerable
• Wide ranging species = large-area
  requirements
• Species with reduced mobility = more
  vulnerable
• Species with low fecundity (related to
  rarity?)
• Species with short life cycle (or multi-
  stage life cycle?)
Habitat Fragmentation: Species-
     Specific Sensitivity?
• Ground-nesting birds may be more
  vulnerable (30-60% reduction in last 25
  yrs)
• Interior-dependent species
• Species vulnerable to human exploitation
  or disturbance
• Specialist species?
Habitat Fragmentation: Species-
     Specific Sensitivity?
Generalizations are a good start
  (= hypotheses?), but a little more
  complex than that……
Gehring and Swihart. 2003.
Biological Conservation
109:283-295
Spatial and Temporal
Ecology of Raccoons

Gehring et al. In prep.
Swihart et al. 2003.
Diversity and
Distributions 9:1-8.
Brown and Litvaitis. 1995. Canadian Journal of Zoology
73:1005-1011
Implications of Changes in Scale
 Insects sampled at 10-m intervals for 100 m

    45
    40
    35
    30
    25                                Predator
    20                                Prey
    15
    10
     5
     0
                    ey
              or

                   Pr
           at
         ed
     Pr
Implications of Changes in Scale
Insects sampled at 2000-m intervals for 20,000 m

     45
     40
     35
     30
     25                               Predator
     20                               Prey
     15
     10
      5
      0
                     ey
               or

                    Pr
            at
          ed
      Pr
                Landscape Pattern
I.        Landscape Components
          (attributes of features or spatial elements)
     A.     Composition
     B.     Configuration
     C.     Connectivity


Relative to landscape spatial elements….
How much of the area is comprised of each type of spatial element?
         How are spatial elements arranged in space?
        How do these attributes change through time?
  How does one quantify landscape pattern?
How do biotic communities interact with pattern?
      Causes of Landscape Pattern
I.     Abiotic Factors
     II. Biotic Factors
     III. Human Landuse
     IV. Disturbance & Succession
  Causes of Landscape Pattern
• Abiotic Factors
  – Variance in climate (biogeographic influences)
  – Variance in landform (more localized constraints;
    microclimates)
Common N.A. trees –
  contractions &
   radiations in
    distribution
Influence of landform – spatial pattern of species distribution
   Causes of Landscape Pattern
• Biotic Factors
  – Competition
  – Predation
  Causes of Landscape Pattern
• Human Land Use
  – Prehistoric, Historic, Present Effects
     • Shift from nomadic hunter-gatherer to farming systems
Human Land Use Practices

1) Agriculture
2) Suburban Development


*Landuse / Landcover Data from
   USGS sources (typically
   resolution to 30 m)
  Causes of Landscape Pattern
• Human Land Use
  – Present Effects
     • Extraction of natural resources
     • Patterns of development
     • Transportation networks
Roads: Formation of Barriers in Landscapes
Clearcuts and National Forest Management
Patch Clearcuts
        Landscape Processes
• Landscape structure influences processes
  such as the flow of energy, materials, and
  species between the ecosystem within a
  landscape.
  Landscape Structure and
Dispersal of Small Mammals
Habitat Patch Size and Isolation
   and Density of Butterfly
          Populations
     Organisms and Landscape
            Structure
• African elephants knock down tress.
  – Change woodland to grassland.
• Kangaroo Rats dig burrow systems that
  modify soil structure and plant distributions.
• Beavers cut trees, build dams and flood
  surrounding landscape.
  – At one time, beavers modified nearly all
    temperate stream valleys in Northern
    Hemisphere.
     Organisms and Landscape
            Structure
• Johnston and Naiman documented
  substantial effects of beavers on landscape
  structure.
  – Over 63 yrs, area created by beavers increased
    from 200 ha to 2,661 ha.
  – Changed boreal forest landscape to complex
    mosaic.
     Organisms and Landscape
            Structure
• Beaver activity between 1927-1988
  increased quantity of most major ions and
  nutrients in impounded areas. Three
  possible explanations:
  – Impounded areas may trap materials.
  – Rising waters captured nutrients formally held
    in vegetation.
  – Habitats created by beavers may promote
    nutrient retention by altering biogeochemical
    processes.
Introduction – Geographical Ecology

• MacArthur defined geographical ecology as
  the search for patterns of plant and animal
  life that can be put on a map.
  – Above level of landscape ecology.
  – Vast breadth
     • Chapter only focuses on a few aspects.
Oceanic Island = Terrestrial Island ?????
Island Area and Species Richness
• Preston found fewest bird species live on
  smallest islands and most species on largest
  islands.
• Nilsson et.al. found island area was best
  single predictor of species richness among
  woody plants, carabid beetles, and land
  snails.
Island Area and Species Richness
   Species-Area Relationship
                   S = cAz
S = # of species
A = island area
 • Positive correlation between island size
   & number of species
• Applies to terrestrial “islands” also
  Habitat Patches on Continents:
        Mountain Islands
• As Pleistocene ended and climate warmed,
  forest and alpine habitats contracted to the
  tops of high mountains across American
  Southwest.
  – Woodlands, grasslands, and desert scrub,
    invaded lower elevations.
  – Once continuous forest converted to series of
    island-like fragments associated with
    mountains: Montane.
             Lakes as Islands
• Lakes can be considered as habitat islands.
  – Differ widely by degree of isolation.
     • Tonn and Magnuson found the number of species
       increases with the area of an insular environment.
     • Barbour and Brown found positive relationship
       between area and fish species richness.
Lakes as Islands
             Marine Islands
• MacArthur and Wilson found isolation
  reduces bird diversity on Pacific Islands.
• Williamson summarized data from
  relationship between island area and species
  richness in Azore Islands:
  – Birds show clear influence of isolation on
    diversity, ferns do not.
  – Land birds fly across water barriers, and ferns
    produce large quantities of light spores easily
    dispersed in the wind.
Marine Islands
 Isolation and Habitat Islands on
            Continents
• Lomolino et.al. found a strong negative
  relationship between isolation and the
  number of montane mammal species living
  on mountaintops across the American
  Southwest.
   Equilibrium Model of Island
          Biogeography
• MacArthur and Wilson: Model explaining
  patterns of species diversity on islands as
  result of immigration and extinction rates.
  – Reasoned rates of immigration would be
    highest on new island with no organisms.
     • As species began to accumulate, rate of immigration
       would decline since fewer arrivals would be new
       species.
   Equilibrium Model of Island
          Biogeography
• Predicted rate of extinction would rise with
  increasing number of species on an island
  for three reasons:
  – Presence of more species creates a larger pool
    of potential extinctions.
  – As number of species increases, population size
    of each must diminish.
  – As number of species increases, potential for
    competitive interactions between species will
    increase.
      Equilibrium Model of Island
             Biogeography
• Point where two lines cross predicts the number of
  species that will occur on an island.
• Proposed rates of extinction on islands would be
  determined mainly by island size.
  – LG near islands will support highest number.
  – SM far islands will support lowest number.
  – SM near and LG far will support intermediate number.
      Island Biogeography
• equilibrium model suggesting that the
  number of species occurring on an
  island represents a balance between
  immigration (in) and extinction (out)
• Robert MacArthur & E.O. Wilson
         Experimental Island
           Biogeography
• Simberloff and Wilson studied insect
  recolonization in Florida Keys.
  – Chose 2 stands of mangroves as control islands,
    and 6 others as experimental islands.
     • Defaunated islands
        – Followed recolonization for 1 yr.
            » Species number stayed constant, but composition
              changed considerably.
Experimental Island
  Biogeography
 Colonization of New Islands by
             Plants
• Rydin and Borgegard found variation in
  spp. richness correlated positively with
  island area and accounted for 44-85% of
  variation in species richness among islands.
  – Small and medium islands continued to
    accumulate species.
  – Large islands attained equilibrium of
    immigration and extinction.
     • Difficult to separate effects of habitat diversity from
       area effects.
     Manipulating Island Area
• Simberloff tested effect of island area on
  species richness.
  – In all cases where area was reduced, species
    richness decreased.
     • Richness on control island increased slightly.
  – Islands with reduced area lost species with each
    reduction in area.
     • Showed area has positive influence on species
       richness.
Manipulating Island Area
   Island Biogeography Update
• Brown and Kodric-Brown found higher
  immigration rates to near islands can reduce
  extinction rates.
• Lomolino found island area can have a
  significant effect on immigration rates.
• Area and isolation are only two of several
  environmental factors affect island species
  richness.
   Latitudinal Gradients in Species
               Richness
• Most groups of organisms are more species-rich
  in the tropics.
• Brown grouped hypotheses into six categories:
  – Time Since Perturbation
     • More species in the tropics because tropics are older and
       disturbed less frequently.
        – More time for speciation, and less frequent disturbance reduces
          extinction rate.
Latitudinal Gradients in Species
            Richness
 – Productivity
    • High productivity contributes to high species
      richness.
       – More energy to divide among population.
 – Environmental Heterogeneity
    • More heterogeneity, thus more potential habitat
      areas and niches.
Latitudinal Gradients in Species
            Richness
– Favorableness
   • Tropics have more favorable environments.
      – No extremes to limit diversity.
– Niche Breadth and Interspecific Interactions
   • Various themes
      – Brown suggests biological processes must play secondary role.
          » Ultimate causes must by physical differences.
 Area and Latitudinal Gradients
      in Species Richness
• Rosenzweig proposed immigration can be
  largely discounted at broad scales, thus
  speciation will be primary source of new
  species.
  – Species removal via extinction.
     • Tropics richness is greater due to higher rates of
       speciation and / or lower rates of extinction.
  Continental Area and Species
           Richness
• Rosenzweig
  found a strong
  positive
  relationship
  between area
  and species
  diversity.

				
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