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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.

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Introduction landscape ecology
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
Vancouver Island marmot(Marmota vancouverensis)

~100 left

Isolated from hoary and

Olympic marmots

Vancouver island marmot marmota vancouverensis1
Vancouver Island marmot(Marmota vancouverensis)

Natural tree succession

Vancouver island marmot marmota vancouverensis2
Vancouver Island marmot(Marmota vancouverensis)

  • Logging – disjunct patches

    • - max. dispersal = 7 km

  • Climate

  • Prey-Predator Dynamics

  • Human Land Use Practices

  • Agriculture

  • 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
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



Formation of

Terrestrial “Islands”

Habitat fragmentation
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”

Patch size


Patch isolation


What about

aquatic systems?

What about

aquatic systems?

Con.Bio 12(6)

Habitat fragmentation1
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

Edge effects
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 fragmentation2
Habitat Fragmentation

  • First-Order Effects: fragmentation leads to change in a species’ abundance and/or distribution

Habitat fragmentation3
Habitat Fragmentation

  • Higher-Order Effects: fragmentation indirectly leads to change in a species abundance and/or distribution via altered species interactions



- Abundance

- Distribution

- Foraging Behaviors


Ground-Nesting Birds

- Abundance

- Distribution

Avian Competitors Avian Prey

Brood Parasites




- Abundance

- Distribution


Habitat fragmentation species specific sensitivity
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 sensitivity1
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 sensitivity2
Habitat Fragmentation: Species-Specific Sensitivity?

  • Generalizations are a good start

  • (= hypotheses?), but a little more complex than that……

Gehring and Swihart. 2003.

Biological Conservation


Spatial and Temporal

Ecology of Raccoons

Gehring et al. In prep.

Implications of changes in scale
Implications of Changes in Scale

Insects sampled at 10-m intervals for 100 m

Implications of changes in scale1
Implications of Changes in Scale

Insects sampled at 2000-m intervals for 20,000 m

Landscape processes
Landscape Processes

  • Landscape structure influences processes such as the flow of energy, materials, and species between the ecosystem within a landscape.

Organisms and landscape structure
Organisms and Landscape Structure Populations

  • 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 structure1
Organisms and Landscape Structure Populations

  • 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 structure2
Organisms and Landscape Structure Populations

  • 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
Introduction – Geographical Ecology Populations

  • 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.

Island area and species richness
Island Area and Species Richness Populations

  • Preston found fewest bird species live on smallest islands and most species on largest islands.

  • Nilsson found island area was best single predictor of species richness among woody plants, carabid beetles, and land snails.


Species area relationship
Species-Area Relationship Populations

  • 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
Habitat Patches on Continents: Mountain Islands Populations

  • 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 as Islands Populations

  • 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 islands1
Lakes as Islands Populations


Marine islands
Marine Islands Populations

  • 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 islands1
Marine Islands Populations


Isolation and habitat islands on continents
Isolation and Habitat Islands on Continents Populations

  • Lomolino 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
Equilibrium Model of Island Biogeography Populations

  • 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 biogeography1
Equilibrium Model of Island Biogeography Populations

  • 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 biogeography2
Equilibrium Model of Island Biogeography Populations

  • 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
Island Biogeography Populations

  • 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
Experimental Island Biogeography Populations

  • 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.


Colonization of new islands by plants
Colonization of New Islands by Plants Populations

  • 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
Manipulating Island Area Populations

  • 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 area1
Manipulating Island Area Populations


Island biogeography update
Island Biogeography Update Populations

  • 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
Latitudinal Gradients in Species Richness Populations

  • 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 richness1
Latitudinal Gradients in Species Richness Populations

  • 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 richness2
Latitudinal Gradients in Species Richness Populations

  • 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
Area and Latitudinal Gradients Populationsin 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
Continental Area and Species Richness Populations

  • Rosenzweig found a strong positive relationship between area and species diversity.