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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In this case, the interpretations of landscape structure could be very different, even though the coefficient of variation is the same. There metrkcs metrics that have been identified that inform about the landscape in its entirety as well as metrics that break down each land cover class within the defined landscape.
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 merrics of spatial heterogeneity of the entire landscape mosaic. Although metircs 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 of patches.
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.
Go to the Fragstats webpage. Thus, mean patch size can serve as a habitat fragmentation index, although the limitations discussed below may reduce its utility in this respect. However, the size of a patch may not be as important as the extensiveness of the patch for some organisms and processes.
In applications that involve comparing landscapes metircs varying size, this index may not be useful. These metrics help us to quantify physical characteristics on the ground and connect them to ecological processes.
However, the maximum value of LSI varies at the class level with class 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 addition, although mean patch size is derived from the number of patches, it does not convey any information about how many patches are present. Variation in patch size may convey more useful information.
Variability is a difficult thing to summarize in a single metric. There is also a stand alone version that can be downloaded. The number of subpopulations could influence the dynamics and persistence of the metapopulation Gilpin and Hanski 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.
The Patch Analystan Esri extension, contains many of the Fragstat 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.
An excellent source for information on landscape metrics are the Fragstats webpages and their associated documentation. Get to know the different types of metrics e. fraystats
For example, the distribution of patch area AREA is fragstate by its mean and variability. For these reasons, mean patch size is merrics best interpreted in conjunction with total class area, patch density fragwtats number of patchesand patch size variability.
Graphic helps to illustrate how landscape metrics can be used to understand environmental metricss and establish thresholds of change.
At the class and landscape levels, edge can be quantified in other ways. This index is similar to the habitat diversity index proposed by Pattonexcept that we apply the index at the class level as well. 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.
Do Go to the Fragstats webpage. Edge density ED standardizes edge to a per unit area basis that facilitates comparisons among landscapes of varying size. Area metrics quantify landscape composition, not landscape configuration.
These differences should be kept in mind when selecting class metrics for a particular application. 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.
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 misleading. LSI is identical to the shape index at the patch level SHAPEexcept that it mefrics based on mtrics area and the associated class perimeter at the class level and the total landscape area and all edges at the landscape level.
Typically metrics are calculated for data classed within a specified landscape your extent. For example, progressive reduction in the size of habitat fragments is a key component of habitat fragmentation. There is a wide variety of metricz metrics that have been developed and applied for many years.
Fragstats and Landscape Metrics | GEOG Conservation GIS
These summary measures provide a way to characterize the distribution of area among patches at the class or landscape level. For example, two landscapes may have the same patch size coefficient of variation, e. In fragstata case, the interpretations of landscape pattern would be very different, even though absolute variation is the same. Therefore, at the class level, these two indices represent slightly different aspects of class structure. This index measures the perimeter-to-area ratio for the landscape as a whole.
Fragstats and Landscape Metrics
However, when comparing classes or landscapes of identical size, total edge and edge density are completely redundant. Skip to main content. Thus, a landscape with a smaller mean patch size for the target patch type than another landscape might be considered more fragmented.
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 both cases, there is no variability in patch size, yet the ecological interpretations could be different.
This is an important characteristic in a number of ecological applications. Thus, it is not necessary to know mean patch size to interpret the coefficient of variation. Alternatively, two landscapes could have the same number 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.
Furthermore, mean patch size represents the average condition.
Patch size coefficient of variation measures relative variability about the mean i. Radius of gyration GYRATE is a measure of patch extent; that is, how far across the landscape a patch extends its reach. 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.
Note, shape complexity and aggregation or contagion are closely related concepts. Riparia, a research Center at Penn State, has been assessing landscape conditions around its more than reference wetland sites.