Landscape Ecology

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Landscape Ecology

• Chapter 21

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Outline

• Introduction
• Landscape Structure
• Landscape Processes
• Habitat Patches and Corridors
• Landscape Position
• Origins of Landscape Structure and Change
• Climate
• Organisms

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Introduction

• Landscape Ecology Study of landscape structure
  and processes.
• Landscape Heterogeneous area composed of several
  ecosystems.
• Landscape Elements Visually distinctive patches
  in an ecosystem.

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Landscape Structure

• Landscape structure includes the size, shape,
  composition, number, and position of different
  ecosystems within a landscape
• Quantified patch shape by ratio of patch
  perimeter to perimeter of a circle with an area
  equal to that of the patch.
• S Patch shape
• Increasing value indicates less circular shape
• P Patch perimeter
• A Patch area

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Landscape Structure
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Fractal Geometry of Landscapes

• Perimeter estimates of a complex shape depend on
  size of measuring device.
• Smaller features may only show up with smaller
  measuring devices.

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Fractal Geometry of Landscapes
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Two components of spatial scale
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Quantifying landscape pattern
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Two principal methods for representing spatial
data
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Caveats for landscape pattern analysis

• Classification scheme

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Caveats for landscape pattern analysis

• Grain size (resolution)

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Caveats for landscape pattern analysis

• Spatial extent

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Caveats for landscape pattern analysis

• Appropriate landscape metrics- most metrics are
  correlated- what constitutes a significant
  change
• References- Riitters, K. H. et al. 1995. A
  factor analysis of landscape pattern and
  structure metrics. Landscape ecology 10 23-39.-
  J. A.G. Jaeger. 2000. Landscape division,
  splitting index, and effective mesh size new
  measures of landscape fragmentation. Landscape
  ecology 15115-130.

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Landscape metrics

• Metrics of landscape composition
• Measures of spatial configuration contagion
  patch-based metrics
• Software for spatial pattern analysis -
  FRAGSTAThttp//www.umass.edu/landeco/research/fra
  gstats/fragstats.html- Patch Analysthttp//flash
  .lakeheadu.ca/rrempel/patch/

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Research tools for landscape ecology

• GPS- Overview http//www.colorado.edu/geography/g
  craft/notes/gps/gps_f.html
• GIS- ESRI http//www.esri.com/
• Remote sensing photogrammetry- SPOT
  http//www.spotimage.fr/html/_167_.php- LiDAR
  http//www.aeromap.com/lidar- Leica Geosystems
  http//www.gis.leica-geosystems.com/default.aspx-
  VLS http//www.featureanalyst.com/index.htm

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Landscape Processes

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

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Landscape Structure and Dispersal of Small Mammals

• Ecologists have proposed landscape structure can
  influence movement of organisms between
  potentially suitable habitats.
• Metapopulations Populations of many species
  occur in spatially isolated patches, with
  significant exchange of individuals.
• Rate of movement of individuals between
  subpopulations can affect species persistence in
  a landscape.

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Landscape Structure and Dispersal of Small Mammals

• Diffendorfer et. al. studied how patch size
  affects movement of three small mammal species.
• Predicted animals would move farther in more
  fragmented landscapes.
• Must move farther to obtain resources.
• Predicted animals would stay longer in more
  isolated patches.

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Landscape Structure and Dispersal of Small Mammals
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Habitat Patch Size and Isolation and Density of
Butterfly Populations

• Hanski et. al. found butterfly density
  significantly affected by size and isolation of
  habitat patches.
• Population size within patch increased with patch
  area.
• Population density decreased as patch area
  increased.
• Isolated patches had lower butterfly densities.
• Population partially maintained by immigration.

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Habitat Patch Size and Isolation and Density of
Butterfly Populations
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Habitat Corridors and Movement of Organisms

• Connecting habitat fragments with corridors of a
  similar habitat has long been an approach to
  mitigating the effects of habitat fragmentation.
• Haddad and Baum found corridors influenced the
  movement of butterflies associated with early
  successional habitats.

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Landscape Position and Lake Chemistry

• Webster explored how lake position in a landscape
  affected chemical responses to drought.
• Lake position in landscape determined portion of
  water received as groundwater.
• Upper lakes dropped more than lower lakes.
• Concentration of dissolved ions increased most at
  upper and lower ends.

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Landscape Position and Lake Chemistry
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Origins of Landscape Structure and Change

• Geological processes such as volcanism,
  sedimentation, and erosion are a primary source
  of landscape structure.

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Soil and Vegetation Mosaics In Sonoran Desert

• McAuliffe showed bajadas in Sonoran Desert are
  complex mosaic of distinctive landforms.
• Found wide range of soil types and plant
  distributions that correspond closely to soil age
  and structure.
• Soil structure influences perennial plant
  distributions.
• Plant distributions map clearly onto soils of
  different ages.

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Soil and Vegetation Mosaics In Sonoran Desert
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Climate and Landscape Structure

• McAuliffe Soil mosaics consisted of patches of
  material deposited during floods originating in
  nearby mountains.
• Materials eroded from mountain slopes and
  deposited as alluvium on surrounding bajadas.
• Alluvial deposits gradually changed dependent
  upon climate.
• Different soils and plant types.

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Organisms and Landscape Structure

• Many studies have focused on conversion of forest
  to agricultural landscapes.
• Eastern NA, many abandoned farms have reverted to
  forest, thus forest cover has increased.
• Similar patterns in parts of Europe.

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Organisms and Landscape Structure

• Hulshoff found forest and heathland coverage
  changed over time as well as number and average
  area of patches.
• Cadiz Township - agricultural economy converted
  area from forest to farmland.
• Economy collapsed in response to introduction of
  synthetic fertilizers and inexpensive imported
  wool.

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Organisms and Landscape Structure
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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.

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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.

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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.

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Fire and Structure of a Mediterranean Landscape

• Minnich used satellite photos to reconstruct fire
  history of S. CA and N. Baja (1971-80).
• Landscape consisted of patchwork of old and new
  burns.
• Similar climates with deviated fire histories
• Fire suppression in S. CA allowed more biomass
  accumulation and resultant large fires.
• Small burns more frequent in N. Baja.
• Other factors

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Review

• Introduction
• Landscape Structure
• Landscape Processes
• Habitat Patches and Corridors
• Landscape Position
• Origins of Landscape Structure and Change
• Climate
• Organisms

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