FRAGSTATS METRICS PDF
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 image on the bottom depicts one way to assess landscape cohesion. For this species, late-seral forest area might be a good index of habitat suitability metrkcs landscapes the size of spotted owl home ranges Lehmkuhl and Raphael Also, note that patch size standard deviation and coefficient of variation can equal 0 under 2 different conditions: I encourage you to explore it! Get to know the different types of metrics e. Fragstats and Landscape Metrics Print There is a wide variety of landscape metrics that have been developed and applied for many years.
For example, the distribution of patch area AREA is summarized by its mean and variability.
In a real landscape, the distribution of patch sizes may be highly irregular. For example, the number or density of patches may determine the number of subpopulations in a spatially-dispersed population, or metapopulation, for species exclusively associated with that habitat type.
Area metrics quantify landscape composition, not landscape configuration. Thus, it is not necessary to know mean patch size to interpret the coefficient mdtrics variation. There are 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.
In many ecological applications, second-order statistics, such as the variation in patch size, may convey more useful information than first-order statistics, such as mean patch size. 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 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. At the landscape level, mean patch size and patch density are both a function of number of patches and total landscape area.
However, when comparing classes or landscapes of identical size, total edge and edge density are completely redundant.
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. 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, holding area constant, the more extensive the patch i. This is an important characteristic in a number of ecological applications.
In contrast, patch density is a function of total landscape area. For example, progressive reduction in the size of habitat fragments is a key component of habitat fragmentation.
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 meetrics. Greater variability indicates less metric 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 the same patch size standard deviation, e. For this reason, many of the shape metrics described here are closely related, at least in concept, to the Contagion metrics described elsewhere.
In this case, the interpretations of landscape structure could be very different, even though the coefficient of variation is the same.
For example, two landscapes could 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. Thus, a landscape with a smaller mean patch size for the target patch type than another landscape might be considered more fragmented. 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.
This is one method to help show where forest habitat corridors might be located.
Thus, although patch size standard deviation conveys information about patch size fdagstats, 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. This index measures the perimeter-to-area ratio for the landscape as a whole. Graphic helps to illustrate how landscape metrics can be used to understand environmental condition and establish thresholds of change. In this case, the interpretations of landscape pattern would be very different, even though absolute variation is the same.
Fragstats and Landscape Metrics | GEOG Conservation GIS
Riparia, a research Center at Penn Fravstats, has been assessing landscape conditions around its more than reference wetland sites. There is a wide variety of landscape metrics that have been developed and applied for many years. Radius of gyration GYRATE is a measure of patch extent; that is, how far across the landscape a patch extends its reach. At the class and landscape levels, edge can be quantified in other ways. These summary measures provide a way to characterize the distribution of area among patches at the class or landscape level.
However, the size of a patch may not be as important as the extensiveness of the patch for some fragstat and processes. 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. Go to the Fragstats webpage. Variability in patch size measures a key aspect of landscape heterogeneity that is not captured by mean patch size and other first-order statistics.
Therefore, at the class level, these two indices represent slightly different aspects of class structure. Alternatively, two landscapes could have the same number of patches and total landscape rfagstats and thus have the same patch density; yet, if class area differed, mean patch size could be very different between landscapes. At the landscape level, metrics are tabulated from within a 1 km radius circle around each site. LSI is identical to the shape index at the patch level SHAPEftagstats 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.
Note, shape complexity and aggregation or contagion are closely related concepts. 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. Skip to main content.
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. In contrast to the class level, these indices are completely redundant assuming there is no internal background. These metrics help us to quantify physical characteristics on the ground and connect them to ecological processes.