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.
Fragstats and Landscape 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. In addition, although many vertebrate species that specialize on a particular habitat have minimum area requirements e.
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.
Similarly, within a single landscape, a patch type with a smaller mean patch size than another patch type might be considered more fragmented. For fragstays, two landscapes may have the same patch size standard deviation, e. 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.
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, the interpretations fragstwts landscape pattern would be very different, even though absolute variation is the same.
A landscape with a greater number or density of patches has a finer grain; that is, mertics spatial heterogeneity occurs at a finer resolution. It may be more informative to inspect the actual distribution itself, rather than relying on summary statistics such as these that make assumptions about the distribution and therefore can be fragsgats.
Riparia, a research Center at Penn State, has been assessing landscape conditions around its more than reference wetland sites.
In contrast to the class level, these indices are completely redundant assuming there is no internal background. Landscape shape index LSI does this.
In applications that involve comparing landscapes of varying size, this index may not be useful. Similarly, holding area constant, the more extensive the patch i. 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. Edge density ED standardizes edge to a per unit area basis that facilitates comparisons among landscapes of varying size.
Note, shape complexity and aggregation or contagion are closely related concepts. However, the maximum value of LSI varies at the class level with class area. Variability in patch size measures a key aspect of landscape heterogeneity that is not captured by mean patch size and other first-order rragstats.
I encourage you to explore it! For example, two landscapes could have the same number and size distribution of patches for a given class and thus have the same fragwtats patch size; yet, if total landscape area differed, patch density could be very different between landscapes.
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 disaggregated i. An excellent source for information on landscape metrics are the Fragstats webpages and their associated documentation.
These metrics usually are best considered as representing landscape configuration, even though they are not spatially explicit measures. This is an important characteristic in a number of ecological applications. For example, the number or density of fragstas may determine the number of subpopulations in a spatially-dispersed population, or metapopulation, for species exclusively associated with that habitat type.
There is also a stand alone mettics that can be downloaded. Familiarize yourself with the details within the metrics.
The number of subpopulations could influence the dynamics and persistence of the metapopulation Gilpin and Hanski 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. In addition, although mean patch size is derived from the number of patches, it does not convey any information about how many patches are present.
Fragstats and Landscape Metrics | GEOG Conservation GIS
The number or density of patches in a 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.
Radius of gyration GYRATE is a measure of patch extent; that is, metrids far across the landscape a patch extends its reach. 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. 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 random starting point.
Typically metrics are calculated for data classed within a specified landscape your extent. Thus, it is not necessary to know mean fragsstats size to interpret the coefficient of variation.
For mwtrics species, late-seral forest area might be a good index of habitat suitability within metdics the size of spotted owl home ranges Lehmkuhl and Raphael When fragstqts 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.
Images show examples of how landscape metrics can be used to quantify condition on land surfaces. Using a moving window focal function, values were assigned to each pixel tabulating the percent fragstate forested pixels within 1 km circle around that pixel. 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 fragstatw or distribution of patches.
For example, consider 2 landscapes with the same patch density and mean patch size, but with very different levels of variation in patch size. Get to know the different types of metrics e. For example, progressive reduction in the size of habitat fragments is a key component of habitat mmetrics. At the landscape level, mean patch size and patch density are both a function of number of patches and total landscape area.
Alternatively, two landscapes could have the same fragstatz of patches and total landscape area and thus have the same patch density; yet, if class area differed, mean patch size could be very different between landscapes. In a real landscape, the distribution of patch sizes may be highly irregular.