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Landscape Ecology

Daijiang Li

LSU

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Announcements

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A landscape is a heterogeneous area consisting of distinct patches (landscape elements) organized into a mosaic-like pattern

A mosaic is the patchwork of different types of land cover/elements (e.g., forests, bogs, meadows, lakes, streams, etc.)

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Landscape Ecology

The study of the causes & consequences of landscape-level (i.e., intermediate- to large-scale) ecological patterns

  • The causes behind the formation of patches and boundaries, and
  • The ecological consequences of these spatial patterns on the landscape
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Landscape Ecology

  • Is concerned with spatial patterns in the landscape and how they develop, with an emphasis on the role of disturbance

  • Is a relatively new branch of ecology

  • Goal: Predict the responses of different organisms to changes in landscape

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Landscape Ecology is the science and art of studying and influencing the relationships between spatial pattern and ecological processes across hierachical levels of biological organization and different scales in space and time
Wu and Hobbs, 2007

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Importance of scale

Landscape ecologists often grapple with issues associated with spatial scale

Two important aspect of spatial scale: grain and extent

Grain refers to the spatial resolution of a study or data set; e.g., are the data or samples obtained at a resolution of 1 m2, 100 m2 or 1 km2?

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Importance of scale

Landscape ecologists often grapple with issues associated with spatial scale

Two important aspect of spatial scale: grain and extent

Grain refers to the spatial resolution of a study or data set; e.g., are the data or samples obtained at a resolution of 1 m2, 100 m2 or 1 km2?

Extent refers to the size of the study area being considered; e.g., is the landscape small or large?

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Importance of scale

Landscape ecologists often grapple with issues associated with spatial scale

Two important aspect of spatial scale: grain and extent

Grain refers to the spatial resolution of a study or data set; e.g., are the data or samples obtained at a resolution of 1 m2, 100 m2 or 1 km2?

Extent refers to the size of the study area being considered; e.g., is the landscape small or large?

No fixed scale, either grain or extent, unambiguously identifies landscape ecology (a landscape ecological approach can also be applied to a very small area with fine resolution)

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Landscape Structure

Landscape structure: the physical configuration of landscape elements, e.g., patch size distributions, patch dispersion, patch shapes, patch connectivity / isolation, etc.

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Patches in the Landscape

  • Patches: relatively homogenous community types that differ from their surroundings in structure (e.g., size, shape) and in species composition
  • Patches result from factors: geology, topography, soils, and climate, human activity
  • The area, shape, and orientation of the landscape patches influence:
    • Habitat suitability
    • Wind flow
    • Dispersal of seeds
    • Movement of animals
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E.g., Lodgepole pine stand age classes (stand ages since last major fire-disturbance) in Yellowstone National Park

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Patches have edges

Some pathces are stable and permanent (inherent edges) while others are subject to successional changes over time (induced edges)

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Inherent edges: Natural edges, caused by changes in soil, topography. E.g., eastern North America – deciduous, coniferous edge

Induced edges: May occur where floods or fires have reversed succession. May occur where humans have created patchwork of tilled land interspersed with fence rows and wood lots

Patches have edges

The height, width, and porosity of borders influence the gradients of wind flow, moisture, temperature, and solar radiation between adjoining patches

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Edge effects: negative (generally) effects of a habitat edge on interior conditions

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Edge effects: negative (generally) effects of a habitat edge on interior conditions

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Some species can only inhabit the interior or core, and some are specifically attracted to the edge

Edge species are restricted exclusively to the edge environment (e.g. Indigo bunting)

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Edge species

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Interior species

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Area-insensitive species

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The edge effect can also create problems: attracts more predator; restricts dispersal, etc.

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Two patches with same area

The shape of a habitat reserve matters! As patches become SMALLER, they become LARGELY EDGE, losing the characteristics of the interior community, e.g., Brown-headed cowbird

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Habitat Loss & Fragmentation

86% of habitat lost of heathland (in England)

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Fragmentation and isolation of heathland (in England) 40,000 ha to 6000 ha in 218 years

1759: 10 large blocks

1978: 1084 pieces

86% of habitat lost.

Habitat Loss & Fragmentation

Loss & fragmentation of U. S. old-growth forests

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Habitat Loss & Fragmentation

The primary cause of loss of biological diversity

  • Loss of habitat

  • Reduced population size

  • Loss of genetic variation

  • Increased edge

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Design Principles for Protected Areas

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The SLOSS Debate

If only a limited amount of habitat can be protected in parks and reserves, which strategy is better: a Single Large reserve Or Several Small reserves (SLOSS)?

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The SLOSS Debate

Several small is better

Ecological Responses to Habitat Fragmentation Per Se

Why do several small patches hold more species than few large patches?

Several small is not better

Is habitat fragmentation good for biodiversity?

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Connectivity and Corridors

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The importance of corridors in fragmented landscapes

Corridors Permit Movement: gene flow, reestablish species (rescue effect) etc.

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Ongoing accumulation of plant diversity through habitat connectivity in an 18-year experiment

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Negative impacts of corridors

  • Scouting positions for predators

  • Disease spread

  • Pathway for the invasion of exotic species

  • If too narrow, can inhibit movement of social groups

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Conservation & Corridors

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Yellowstone 2 Yukon https://y2y.net/

Strategy is based on conservation requirements of grizzly bears.

Secondary focus on bird & fish species.

Priority areas: core wildlife habitat OR key corridors connecting core areas

Work with scientists, agencies, Aboriginal communities, land trusts, & some businesses.

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Yellowstone 2 Yukon

Does Y2Y want the entire region to become a protected area or park?

No. Y2Y's vision is that the Y2Y region will be managed so that this world-renowned mountain ecosystem and its inhabitants (wild & human) remain healthy and connected for centuries to come.

This requires that wild animals are able to travel safely through land adjacent to and between parks.

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Scaling populations to landscapes (metapopulation)

Species-area relationships (to be covered in the Macroecology lectures)

The theory of island biogeography (to be covered in the Macroecology lectures)

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Announcements

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