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Why Quantify Landscape Pattern?

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

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Why Quantify Landscape Pattern?

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  1. Why Quantify Landscape Pattern? • Comparison (space & time) • Study areas • Landscapes • Inference • Agents of pattern formation • Link to ecological processes

  2. Programs for Quantifying Landscape Pattern • FRAGSTATS • http://www.umass.edu/landeco/research/fragstats/documents/Metrics/Metrics%20TOC.htm • Patch Analyst • http://flash.lakeheadu.ca/~rrempel/patch/

  3. 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.)

  4. 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

  5. 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)

  6. Quantifying Pattern: Corridors • Internal: • Width • Contrast • Env. Gradient • External: • Length • Curvilinearity • Alignment • Env. Gradient • Connectivity (gaps)

  7. 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

  8. Quantifying Pattern: Patches • Composition: • Variety & abundance of elements • Configuration: • Spatial characteristics & dist’n of elements

  9. Quantifying Pattern: Patches • Composition: • Mean (or mode, median, min, max) • Internal heterogeneity (var, range) • Spatial Characters: • Area (incl. core areas) • Perimeter • Shape

  10. 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

  11. Quantifying Pattern: Patches • Configuration: • Patch Size & Density • Mean patch size • Patch density • Patch size variation • Largest patch index

  12. 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

  13. Quantifying Pattern: Patches • Configuration: • Core Area (interior habitat) • # core areas • Core area density • Core area variation • Mean core area • Core area index

  14. Quantifying Pattern: Patches, Zonal • Configuration: • Isolation / Proximity • Proximity index • Mean nearest neighbor distance

  15. Proximity Index (PXi) = measure of relative isolation of patches; high (absolute) values indicate relative connectedness of patches

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