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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Radius of gyration GYRATE is a measure of fragstas extent; that is, how far across the landscape a patch extends its reach. 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.
Fragstats and Landscape Metrics | GEOG Conservation GIS
Using a moving window focal function, values were assigned to each pixel tabulating the percent of forested pixels within 1 km circle around that pixel.
For example, metrucs important by-product of habitat fragmentation is habitat loss. In contrast, patch density is a function of total landscape area. Mean patch size at the class level is a function of the number of patches in the class and total class area. 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 meetrics or radius of gyration at the class and landscape levels.
Fragstats and Landscape Metrics
Fragstats and Landscape Metrics Print There is a wide variety of landscape metrics that have been developed and applied for many years. An excellent source for information on landscape metrics are the Fragstats webpages and their associated fraagstats. The number of subpopulations could influence the dynamics and persistence of the metapopulation Gilpin and Hanski The image on the bottom depicts one way to assess landscape cohesion.
However, the size of a patch may not be as important as the extensiveness of the patch for some organisms and processes. In this case, the interpretations of landscape pattern would be very different, even though absolute variation is the same. 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 metrlcs index of spatial heterogeneity of the entire landscape mosaic.
There are metrics that have been identified that inform about the landscape in its entirety as well as metrics that break cragstats each land cover class within the defined landscape. I encourage mefrics to explore it!
Similarly, within a single landscape, a patch type with a smaller mean patch size than another patch type might be considered more fragmented. 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 Riparia, a research Center at Penn State, has been assessing landscape conditions around its more than reference wetland sites.
Variability in patch size measures a key aspect of landscape heterogeneity that is not captured by mean patch size and other first-order statistics.
It is important to keep in mind that both standard deviation and coefficient of variation feagstats a normal distribution about the mean.
Furthermore, mean patch size represents the average condition.
Images show examples of how landscape metrics can be metricw to quantify condition on land surfaces. This index measures the perimeter-to-area ratio for the landscape as a whole. 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.
Ultimately, the choice of standard deviation or coefficient of metrids will depend on whether absolute or relative variation is more meaningful in a particular application. Variation in patch size may convey more useful information.
The Patch Analystan Esri extension, contains many of the Fragstat metrics. At the landscape level, metrics are tabulated from within a 1 km radius circle around each site.
Graphic helps to illustrate how landscape metrics can be fragstqts to understand environmental condition and establish thresholds of change. 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. Greater variability indicates less uniformity in pattern either at the class level or landscape level and may reflect differences in underlying processes affecting the landscapes.
For example, two landscapes may have dragstats same patch size standard deviation, e. In addition to these primary metrics, FRAGSTATS also summarizes the distribution of patch area and meyrics radius of gyration across all patches at the class and landscape levels. 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 the class level and the total landscape area and all edges at the landscape level.
In addition to its direct interpretive value, class area in absolute or relative terms is used in the computations for many of the class and landscape metrics. It may be more informative to inspect the actual distribution itself, rather than relying on summary statistics such as these fragstars make assumptions about the distribution and therefore can be misleading.