Transcript Why Quantify Landscape Pattern?

Why Quantify Landscape
Pattern?
• Often have hypotheses relating
pattern to ecological processes
• Describe change over time
• Compare different landscapes
Changes in forest cover (shaded
green) since the time of
European settlement for Cadiz
Township in southeastern
Wisconsin. This pattern can be
observed in many areas and
illustrates both the changes in
the abundance and spatial
arrangement of forest in the
landscape.
From Turner, Gardner, and O’Neill 2002
Changes in conifer (green) and
other forest types for a private
and public landscape (2,500 ha)
with similar initial conditions and
rates of change that are
relatively high for the ownership
types. Landscape metrics were
used to quantify the differences
in landscape pattern between
ownerships.
From Turner, Gardner, and O’Neill 2002
What is landscape pattern?
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Number of types
Proportion of each type on the landscape
Spatial arrangement of patches
Patch shape
Contrast between neighboring patches
Two principal methods for representing spatial data in a GIS: vector-based representation and
raster, or cell-based, representation.
From Turner, Gardner, and O’Neill 2002
Basic components of metrics
• Fraction or proportion (p) of landscape
occupied
• Number of land cover classes present
• Probabilities of adjacency among classes
• Contagion or ‘clumpiness’ within a class
Basic components of metrics—patch
based
• Patch area or size
• Patch perimeter
• Connectivity/fragmentation within a cover
type class (e.g., mean interpatch distance)
• Patch shape and edge characteristics
Caveats for landscape pattern
analysis
Landscape classification scheme
all-important
Examples of how the same landscape looks very different under different classification schemes.
Both panels show how a 5- by 5-km section (100 grid cells) of southwestern Yellowstone
National Park. (a) The landscape is classified based on forest community composition. (b) The
landscape is classified based on successional stage of the forest stands.
From Turner, Gardner, and O’Neill 2002
From Turner, Gardner, and O’Neill 2002
• Goals and objectives must precede
calculations
Scale must be defined- grain and
extent
Effects of changing extent on a landscape of southwestern Yellowstone National Park. Note that
the presence and relative proportions of the different land-cover types change as the extent of
the map varies.
From Turner, Gardner, and O’Neill 2002
From Turner, Gardner, and O’Neill 2002
Definition of what constitutes a ‘patch’
matters
Identification of patches (shaded) on the same map using either (a) a four-neighbor rule, in
which the horizontal and vertical neighbors are considered, but the diagonal neighbors are not,
and (b) an eight-neighbor rule, in which the horizontal, vertical, and diagonal neighbors are all
considered.
From Turner, Gardner, and O’Neill 2002
Most metrics are correlated
One index is not sufficient--but how
many?
Three-dimensional pattern
space in which three subregions
of the southeastern United
States are characterized by
three landscape metrics.
From Turner, Gardner, and O’Neill 2002
Major limitation of any indices—
information lost
A useful set of metrics-• Are selected for a particular objective
• Measured values are well-distributed over
range
• Metrics are relatively independent
Research still needed—
• Relation of metrics/pattern to process
• Sensitivity of similar metrics for detecting
change
• Statistical and sampling properties of
metrics
From Turner, Gardner, and O’Neill 2002
Garden City, Kansas
Image taken 9/25/2000
Center pivot irrigation
systems create red circles
of healthy vegetation in this
image of croplands near
Garden City, Kansas.
Garden City can be found
on Landsat 7 WRS Path 30
Row 34, center: 37.48, 100.51.
US Geological Survey/NASA http://astroboy.gsfc.nasa.gov/earthasart/index.html
From Mladenoff et al. 1993
From Mladenoff et al. 1993
From Mladenoff et al. 1993
From Mladenoff et al. 1993
From Mladenoff et al. 1993
From Mladenoff et al. 1993
Florida Everglades
Image taken 2/5/2000
Spanning the southern tip
of the Florida Peninsula
and most of Florida Bay,
Everglades National Park is
the only subtropical
preserve in North America.
It contains both temperate
and tropical plant
communities, including
sawgrass prairie, mangrove
and cypress swamps,
pinelands, and hardwood
hammocks, as well as
marine and estuarine
environments. The park is
known for its rich bird life,
particularly large wading
birds, such as the roseate
spoonbill, wood stork, great
blue heron, and a variety of
egrets. It is also the only
place in the world where
alligators and crocodiles
exist side by side.
The Everglades can be
found on Landsat 7 WRS
Path 15 Row 42, center:
26.00, -80.43.
US Geological Survey/NASA http://astroboy.gsfc.nasa.gov/earthasart/index.html