Introduction landscape ecology
Sponsored Links
This presentation is the property of its rightful owner.
1 / 71

Introduction – Landscape Ecology PowerPoint PPT Presentation

  • Updated On :
  • Presentation posted in: General

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.

Download Presentation

Introduction – Landscape Ecology

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

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

  • 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

  • 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



Roads: Formation of Barriers in Landscapes

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

Patch size


Patch isolation


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



- Abundance

- Distribution

- Foraging Behaviors


Ground-Nesting Birds

- Abundance

- Distribution

Avian Competitors Avian Prey

Brood Parasites




- Abundance

- Distribution


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


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


Implications of Changes in Scale

Insects sampled at 10-m intervals for 100 m

Implications of Changes in Scale

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

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 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 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 Gradientsin 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.


  • Login