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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For example, the distribution of patch area AREA is summarized by its mean and variability. 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.
For example, progressive reduction in the size of habitat fragments is a key component of habitat fragmentation. Note, shape complexity and aggregation or contagion are closely related concepts.
Fragstats and Landscape Metrics
Ultimately, the choice of standard deviation or coefficient of variation will depend on whether absolute or relative variation is more meaningful in a particular application. Edge metrics usually are best considered as representing landscape configuration, even though they are not spatially explicit at all.
These metrics help us to quantify physical characteristics on the ground and connect them to ecological processes. This is an important characteristic in a number of ecological applications.
In addition to these primary metrics, FRAGSTATS also summarizes the distribution of patch area and extent radius of gyration across all patches at the class and landscape levels.
For example, two landscapes may have the same patch size coefficient of variation, e. Do Go to the Fragstats webpage. Often landscape metrics act as surrogates for conditions that cannot be directly measured. At the landscape level, mean patch size and patch density are both a function of number of patches and total landscape area. 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.
A landscape with a greater number or density of patches has a finer grain; that is, the spatial heterogeneity occurs at a finer resolution. At the class and landscape levels, edge can be quantified in other ways.
Fragstats and Landscape Metrics | GEOG Conservation GIS
Furthermore, mean patch size represents the metgics condition. Thus, a landscape with a smaller mean patch size for the target patch type than another landscape might be considered more fragmented.
In addition, although many vertebrate species that specialize on a particular habitat have minimum area requirements e.
However, when comparing classes or landscapes of identical size, total edge and edge density are completely redundant. Although both indices may be useful for “describing” 1 or more landscapes, they would never be used simultaneously in a statistical analysis of landscape structure.
In addition, although mean patch size is derived from the number of patches, mefrics does not convey any information about how many patches are present. In contrast, patch fragstatw is a function of total landscape area. For example, a mean patch size of 10 ha could represent a class with 5 ha patches or a class with 2- 3- 5-,and ha patches, and this difference could be important ecologically.
In both cases, there is no variability in patch size, yet the ecological interpretations could be different. The image on the bottom depicts one way to assess landscape cohesion.
At the landscape level, metrics are tabulated from within a 1 km radius circle around each site. The number of subpopulations could influence the dynamics and persistence of the metapopulation Gilpin and Hanski For example, two landscapes could have the same number and size distribution of patches fragstars a given class and thus have the same mean patch size; yet, if total landscape area differed, patch fragsrats could be very different between landscapes.
Because these measures are not wholly redundant, it may be meaningful to interpret both measures in some applications. Graphic helps to illustrate how landscape metrics can be used to understand environmental condition and establish thresholds of change. All other metricw equal, the larger the patch, the larger the radius of metrifs.
Typically metrics are calculated for data classed within a specified landscape your extent. In contrast to the class level, these indices are completely redundant assuming there is no internal background. Variation in patch size may convey more useful information.
Riparia, a research Center at Penn State, has been assessing landscape conditions around its more than reference wetland sites. FRAGSTATS computes several simple statistics representing the number or density of patches, the average size or radius of gyration of patches, and the variation in patch size or radius of gyration at the class and landscape levels.
Also, note that patch size standard deviation and coefficient of variation can equal 0 under 2 different conditions: This index measures the perimeter-to-area ratio for the landscape as a whole. 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 There is a wide variety of landscape metrics that have been developed and applied for many years.
Edge density ED standardizes edge to a per unit area metris that facilitates comparisons among landscapes of varying size. 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 efficiently completed.
Patch size coefficient of variation measures relative variability about the mean i. Holding area constant, as shape complexity increases as measured by any of the perimeter-area ratio measures described above the patch, class, or entire patch mosaic becomes increasingly fragstatw i.
As noted above, the area AREA of each patch comprising a landscape mosaic is perhaps the single most important and useful piece of information contained in the landscape.
However, the maximum value of LSI varies at the class level with class area. For example, northern spotted owls have minimum area requirements for late-seral forest that varies geographically; yet, individual spotted owls use late-seral forest that may be distributed among many patches Forsman et al.
For example, consider 2 landscapes with the same patch density and mean patch size, but with very different levels of variation in patch size. These metrics usually are best considered as representing landscape configuration, even though they are not spatially explicit measures.
A mean patch size of 10 ha could represent 1 or patches and the difference could have profound ecological implications. 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 metrivs starting point.
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. For this reason, many of the shape metrics described here are closely related, at least in concept, to the Contagion metrics described elsewhere.
Alternatively, the amount of edge present in a class or landscape fragstat 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. For this species, late-seral forest area might be a good index of habitat suitability within landscapes the size of spotted owl home ranges Lehmkuhl and Raphael