These metrics usually are best considered as representing landscape configuration, In addition to these primary metrics, FRAGSTATS also summarizes the. There is a wide variety of landscape metrics that have been developed and applied for many years. These metrics help us to quantify physical characteristics on. every patch is counted; FRAGSTATS does not sample patches from the . For a categorized list of FRAGSTATS output metrics see the FRAGSTATS Metrics.
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The number or density of patches also can alter the stability of species interactions and opportunities for coexistence in both predator-prey and competitive systems Kareiva In this case, fargstats interpretations of landscape structure could be very different, even though the coefficient of variation is the same. Riparia, a research Center at Penn State, has been assessing landscape conditions around its more than reference wetland sites.
Also, note that patch size standard deviation and coefficient of variation can equal 0 under 2 different conditions: The image on the bottom depicts one way fragstaats assess landscape cohesion. The minimum value of LSI is always equal to 1 when either the class is maximally compact at the class level or the landscape consists of a single patch at the landscape level.
The number or density of patches in fragstxts landscape mosaic pooled across patch types can have the same ecological applicability, but more often serves as a general index of spatial heterogeneity of the entire landscape mosaic.
For example, consider 2 landscapes with the same metricss density and mean patch size, but with very different levels of variation in patch size. Because these measures are not wholly redundant, it may be meaningful to interpret both measures in some applications. For example, progressive reduction in the size metrlcs habitat fragments is a key component of habitat fragmentation.
At the class and landscape levels, edge can be quantified in other ways. These differences should be kept in mind when selecting class metrics for a particular application. For these reasons, mean patch size is probably best interpreted in conjunction with total class area, patch density or number of patchesand patch size variability. LSI is identical to the shape index at the patch level SHAPEexcept that it is based on class area and the associated class perimeter at frabstats class level and the total landscape area and all edges at the landscape level.
Mean patch size at the class level is a function of the number of patches in the class and total class area.
Variability is a difficult thing to summarize in a single metric. Alternatively, the amount of edge present in a class or landscape can be compared to that expected for a maximally compact class or landscape of the same size but with a simple geometric shape square and no internal edge, respectively. Nevertheless, patch size coefficient of variation also can be misleading with fragsrats to landscape structure in the absence of information on the number of patches or patch density and other structural characteristics.
Furthermore, netrics patch size represents the average condition. 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. Although the number or density of patches in a class or in the landscape may be fundamentally important to a number of ecological processes, often it does not have any interpretive value by itself because it conveys no information about the area or distribution fragsttats patches.
A landscape with a greater number or density of patches has a finer grain; that is, the spatial heterogeneity occurs at a finer resolution. 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. For this reason, many of the shape metrics described here are closely related, at least in concept, to the Contagion metrics described elsewhere.
In a real landscape, the distribution of patch sizes may be highly irregular.
Variation in patch size may convey more useful information. There is a wide variety of landscape metrics that have been developed and applied for many years. Class area CA and percentage of landscape PLAND are frafstats of landscape composition; specifically, how much of the landscape is comprised of a particular patch type.
Thus, mean patch size can serve as a habitat fragmentation index, although the limitations discussed below may reduce its utility in this respect.
Number or density of patches is probably most valuable, however, as the basis for computing other, more interpretable, metrics. In this case, the interpretations of landscape pattern would be very different, even though absolute variation is the same.
Metrids example, an important by-product of habitat fragmentation is habitat loss. In addition, although many vertebrate species that specialize on a particular habitat have minimum area requirements e.
Radius of gyration GYRATE is a measure of patch extent; that is, how far across the landscape a patch extends its reach. Area metrics quantify landscape composition, not landscape configuration. Graphic helps to illustrate how landscape metrics can be used to understand environmental condition and establish thresholds tragstats change.
Fragstats and Landscape Metrics
Go to the Fragstats webpage. Edge density ED standardizes edge to a per unit area basis that facilitates comparisons among landscapes of varying size. Skip to main content. In applications that involve comparing landscapes of varying size, this index may not be useful.
Fragstats and Landscape Metrics | GEOG Conservation GIS
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. In the study of forest fragmentation, therefore, it is important to know how much of the target patch type habitat exists within the landscape.
For example, two landscapes mehrics have the same number and size distribution of patches for a given class and thus have the same mean patch size; yet, if total landscape area differed, patch density could be very different between landscapes. Edge metrics usually are best considered as representing landscape configuration, even though they are not spatially explicit at all. A mean patch size of 10 ha could represent 1 or patches and the difference could have metgics ecological implications.
Fragstats software McGarigal and Marks was one of the first attempts to package many metrics into an organized software so that processing metrics could be more merics completed.
Familiarize yourself with the details within the metrics. Thus, although patch size standard deviation conveys information about patch size variability, it is a difficult parameter to interpret without doing so in conjunction with mean patch size because the absolute variation is dependent on mean patch size.
Similarly, within a single landscape, a patch type with a smaller mean patch size than another patch type might be considered more fragmented. However, the size of a patch may not be as important as the extensiveness of the patch for some organisms and processes. Landscape shape index LSI does this. I encourage you to explore it! For example, two landscapes may have the same patch size standard deviation, e.
