Quantification of a landscape, or describe landscape in a meaningful and quantitative way. Number of Patches ? Average Patch Size ? Patch Density ? Edge Index ? …

Urban

Wetland

Coniferous Forest

Mixed Forest

What is FRAGSTATS FRAGSTATS is a spatial pattern analysis program for categorical maps. The landscape subject to analysis is userdefined and can represent any spatial phenomenon. FRAGSTATS quantifies the areal extent and spatial configuration of patches within a landscape. It is incumbent upon the user to establish a sound basis for defining and scaling the landscape (including the extent and grain of the landscape) and the scheme upon which patches are classified and delineated. The output from FRAGSTATS is meaningful only if the landscape mosaic is meaningful relative to the phenomenon under consideration.

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Questioning before using FRAGSTATS? • Will the thematic information meet the requirements of the project? • Are the minimum mapping unit meet the requirements of the project? • Where the data come from and have the data been validated? • Is the scale appropriate? • ……

Digital image classification

Visual interpretation and manual delineation

(USGS Level II)

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A Subset of Land Use and Land Cover Map Near URI

(USGS Level II)

A Subset of Land Use and Land Cover Map Near URI

(USGS Level I)

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Extent is the overall area encompassed by an investigation or the area included within the landscape boundary. From a statistical perspective, the spatial extent of an investigation is the area defining the population we wish to sample. Grain is the size of the individual units of observation. For example, a fine-grained map might structure information into 1-ha units, whereas a map with a coarser resolution would have information structured into 10-ha units. Extent and grain define the upper and lower limits of resolution of a study. Any inferences about scale-dependency in a system are constrained by the extent and grain of investigation.

FRAGSTATS computes 3 groups of metrics. • Patch-level – nature of patches, i.e., each patch in the mosaic (.patch), e.g., average size, size of core area … • Class-level – nature of each type, i.e., each class (patch type) in the mosaic (.class), e.g., amount and distribution of each type • Landscape-level – nature of the landscape, i.e., the landscape mosaic as a whole (.land), e.g., pattern, configuration of entire mosaic, landscape diversity, heterogeneity Urban Coniferous Forest Wetland Mixed Forest

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FRAGSTATS also computes the adjacency matrix (i.e., tally of the number of cell adjacencies between each pairwise combination of patch types), which is used in the computation of several class- and landscape-level metrics.

Landscape Composition refers to features associated with the variety and abundance of patch types within the landscape, but without considering the spatial character, placement, or location of patches within the mosaic. Because composition requires integration over all patch types, composition metrics are only applicable at the landscape-level. Quantitative measures of landscape composition: e.g., • proportion of the landscape in each patch type • patch richness • patch evenness • abundance • patch diversity

Urban Coniferous Forest Wetland Mixed Forest

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Landscape Configuration refers to the spatial character and arrangement, position, or orientation of patches within the class or landscape. • • • • • •

Size distribution Density Core/edge area Shape complexity Isolation/proximity Dispersion/connectivity

Urban Coniferous Forest Wetland Mixed Forest

Configuration can be quantified in terms of the landscape unit itself (i.e., the patch).

Shape Index • Complexity of the patch shape relative to a square of the same size

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Isolation/Proximity • Spatial context of patches (rather than the patches themselves)

Contagion • Landscape texture • Tendency for cell types to be spatially aggregated, dispersed • Are cells of similar patches aggregated?

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Connectivity • Degree to which a landscape facilitates or impedes flow • How connected is a particular type/class?

Scale Consideration FRAGSTATS does not limit the scale (extent or grain) of the landscape subject to analysis. The distance- and area-based metrics are reported in meters and hectares, respectively. FRAGSTATS outputs data files in ASCII format that can be manipulated using database management programs to rescale metrics or to convert them to other units.

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FRAGSTATS Metrics The area (AREA) of each patch is an important and useful piece of information contained in the landscape. However, the size of a patch may not be as important as the extensiveness of the patch for some organisms and processes.

FRAGSTATS Metrics Class area (CA) and percentage of landscape (PLAND) are measures of landscape composition; specifically, how much of the landscape is comprised of a particular patch type. This is an important characteristic in a number of ecological applications. For example, how much of the target patch type (habitat) exists within the landscape in association with habitat requirements (fragmentation, isolation, minimum area, etc.)? In addition to its direct interpretive value, class area is used in the computations for many of the class and landscape metrics.

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FRAGSTATS Metrics Radius of gyration (GYRATE) is a measure of patch extent; that is, how far across the landscape a patch extends its reach. All other things equal, the larger the patch, the larger the radius of gyration. Similarly, holding area constant, the more extensive the patch (i.e., elongated and less compact), the greater the radius of gyration.

FRAGSTATS Metrics The radius of gyration can be considered a measure of the average distance an organism can move within a patch before encountering the patch boundary from a random starting point. When aggregated at the class or landscape level, radius of gyration provides a measure of landscape connectivity (known as correlation length) that represents the average traversability of the landscape for an organism that is confined to remain within a single patch.

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FRAGSTATS Metrics Number of patches (NP) or patch density (PD) of a particular habitat type may affect a variety of ecological processes, depending on the landscape context. For example: Those may • determine the number of subpopulations in a spatially-dispersed population for species exclusively associated with that habitat type; • alter the stability of species interactions and opportunities for coexistence in both predator-prey and competitive systems; • can serve as general indices of spatial heterogeneity of the landscape mosaic • …

Number or density of patches is probably most valuable as the basis for computing other more interpretable metrics.

FRAGSTATS Metrics Reduction in the size of habitat fragments is a key component of habitat fragmentation. A landscape with a smaller mean patch size for the target patch type than another landscape might be considered more fragmented. Thus, mean patch size can serve as a habitat fragmentation index.

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FRAGSTATS Metrics Mean patch size at the class level is a function of the number of patches in the class and total class area. In contrast, patch density is a function of total landscape area. Therefore, at the class level, these two indices represent slightly different aspects of class structure. For example, two landscapes could have the same number and size distribution of patches for a given class and thus have the same mean patch size. If total landscape area differed, patch density could be very different between landscapes.

FRAGSTATS Metrics Alternatively, two landscapes could have the same number of patches and total landscape area and thus have the same patch density. If class area differed, mean patch size could be very different between landscapes. These differences should be kept in mind when selecting class metrics for a particular application.

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FRAGSTATS Metrics FRAGSTATS computes several statistics representing the amount of perimeter (or edge) at the patch, class, and landscape levels. Edge metrics usually are best considered as representing landscape configuration, even though they are not spatially explicit.

FRAGSTATS Metrics At the patch level, edge is a function of patch perimeter (PERIM). At the class and landscape levels, Total edge (TE) is an absolute measure of total edge length of a particular patch type (class level) or of all patch types (landscape level). Edge density (ED) standardizes edge to a per unit area basis that facilitates comparisons among landscapes of varying size. However, when comparing classes or landscapes of identical size, total edge and edge density are completely redundant.

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FRAGSTATS Metrics Landscape shape index (LSI) measures the perimeter-to-area ratio for the landscape as a whole. LSI is identical to the shape index at the patch level (SHAPE), except that it is based on class area and the associated class perimeter at the class level and the total landscape area and all edges at the landscape level. FRAGSTATS also computes a normalized landscape shape index (nLSI) in which the metric is rescaled by the minimum and maximum values.

Limitations of FRAGSTATS Metrics All edge indices are affected by the resolution of source images for mapping. Generally, the finer the resolution, the greater the edge length. At coarse resolutions, edges may appear as relatively straight lines; whereas, at finer resolutions, edges may appear as highly convoluted lines. Values calculated for edge metrics should not be compared among images with different resolutions.

30-meter Spatial Resolution

2-meter Spatial Resolution

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Limitations of FRAGSTATS Metrics Patch perimeter and the length of edges will be biased in raster images because of the stair-step patch outline, i.e. the measured edge length is always more than the true edge length. This will affect all edge indices. The magnitude of this bias will vary in relation to the grain or resolution of the image. The consequences of this bias with regards to the interpretation and use of these indices must be weighed relative to the phenomenon under investigation.

Check FRAGSTATS documentations and HELP files for more details on: • • • • • • • •

Shape Metrics Core Area Metrics Isolation/Proximity Metrics Contrast Metrics Contagion/Interspersion Metrics Connectivity Metrics Diversity Metrics ……

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Output Files Depending on which metrics are selected by the user, FRAGSTATS creates 4 output files corresponding to the three levels of metrics and the adjacency matrix. The user supplies a "basename" for the output files and FRAGSTATS appends the extensions .patch, .class, .land and .adj to the basename. These files are formatted to facilitate input into spreadsheets and database management programs:

Output Files • "basename".patch file.–Contains the patch metrics; the file contains 1 record (row) for each patch in the landscape; columns represent the selected patch metrics.

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Output Files • "basename".patch file.–Contains the patch metrics; the file contains 1 record (row) for each patch in the landscape; columns represent the selected patch metrics.

CSD = Standard Deviations from the Class Mean CPS = Percentile of the Class Distribution LSP = Percentile of the Landscape Distribution LPS = Landscape level percentile PERIM = Patch Perimeter PERM_CSD = Patch perimeter standard deviation

Output Files "basename".class file.–Contains the class metrics; the file contains 1 record (row) for each class in the landscape; columns represent the selected class metrics.

CA = Total (Class) Area PLAND = Percentage of Landscape LPI = Largest Patch Index TE = Total Edge AREA_MN = Area Mean AREA_AM = Area weighted mean AREA_MD = Area Median

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Output Files "basename".land file.–Contains the landscape metrics; the file contains 1 record (row) for the landscape; columns represent the selected landscape metrics.

TA = Total Area LPI = Largest Patch Index TE = Total Edge ED = Edge Density AREA_MN = Area Mean AREA_AM = Area weighted mean AREA_MD = Area Median AREA_RA = Area Range AREA_SD = Area standard deviation

Output Files “basename”.adj file.–Contains the class adjacency matrix; the file contains a simple header in addition to 1 record (row) for each class in the landscape, and is given in the form of a 2-way matrix. Specifically, first record contains the input file name, including the full path. The second record and first column contain the class IDs (i.e., the grid integer values associated with each class), and the elements of the matrix are the tallies of cell adjacencies for each pairwise combination of classes. ID

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1

4

2

3

3436

223

1243

260

1

223

1652

160

26

4

1243

160

5506

155

2

260

26

155

566

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