Transcript Document

Why Quantify Landscape Pattern?
• Comparison
(space & time)
– Study areas
– Landscapes
• Inference
– Agents of pattern
formation
– Link to ecological
processes
Programs for Quantifying Landscape
Pattern
• FRAGSTATS
– http://www.umass.edu/lan
deco/research/fragstats/do
cuments/Metrics/Metrics
%20TOC.htm
• Patch Analyst
– http://flash.lakeheadu.ca/~
rrempel/patch/
Quantifying Landscape Pattern
• Just because one can measure it, doesn’t
mean one should
– Does the metric make sense?...biologically
relevant?
– Avoid correlated metrics
– Cover the bases (comp., config., conn.)
Landscape Metrics - Considerations
• Selecting Metrics……
– Subset of metrics needed that:
• i) explain (capture) variability in pattern
• ii) minimize redundancy (i.e., correlation among
metrics = multicollinearity)
– O’Neill et al. (1988) Indices of landscape
pattern. Landscape Ecology 1:153-162
• i) eastern U.S. landscapes differentiated using
– dominance
– contagion
– fractal dimension
Landscape Metrics - Considerations
• Selecting Metrics……
– Use species-based metrics
– Use Principal Components Analysis (PCA)?
– Use Ecologically Scaled Landscape Indices
(ESLI; landscape indices, scale of species, and
relationship to process)
Quantifying Pattern: Corridors
• Internal:
– Width
– Contrast
– Env. Gradient
• External:
–
–
–
–
–
Length
Curvilinearity
Alignment
Env. Gradient
Connectivity (gaps)
Quantifying Pattern: Patches
• Levels:
– Patch-level
• Metrics for indiv.
patches
– Class-level
• Metrics for all patches
of given type or class
– Zonal or Regional
• Metrics pooled over 1
or more classes within
subregion of landscape
– Landscape-level
• Metrics pooled over all
patch classes over entire
extent
Quantifying Pattern: Patches
• Composition:
– Variety & abundance
of elements
• Configuration:
– Spatial characteristics
& dist’n of elements
Quantifying Pattern: Patches
• Composition:
– Mean (or mode,
median, min, max)
– Internal heterogeneity
(var, range)
• Spatial Characters:
– Area (incl. core areas)
– Perimeter
– Shape
Quantifying Pattern: Landscapes
(patch based)
• Composition:
– Number of patch type
• Patch richness
– Proportion of each type
• Proportion of landscape
– Diversity
• Shannon’s Diversity Index
• Simpson’s Divesity Index
– Evenness
• Shannon’s Evenness
Index
• Simpson’s Index
Quantifying Pattern: Patches
• Configuration:
– Patch Size & Density
• Mean patch size
• Patch density
• Patch size variation
• Largest patch index
Quantifying Pattern: Patches
• Configuration:
– Shape Complexity
• Shape Index
• Fractal Dimension
• Fractals = measure of
shape complexity (also
amount of edge)
• Fractal dimension (d)
ranges from 1.0 (simple
shapes) to 2.0 (more
complex shapes)
• ln(A)/ln(P), where A =
area, P = perimeter
Quantifying Pattern: Patches
• Configuration:
– Core Area (interior
habitat)
• # core areas
• Core area density
• Core area variation
• Mean core area
• Core area index
Quantifying Pattern: Patches, Zonal
• Configuration:
– Isolation / Proximity
• Proximity index
• Mean nearest
neighbor distance
•
Proximity Index (PXi) = measure of relative
isolation of patches; high (absolute) values
indicate relative connectedness of patches