For this final tutorial post, I’ll be describing a workflow in which FRAGSTATS is used to generate a number of continuous metrics of disturbance patches. Then, using these metrics, a Grouping Analysis is performed in ArcMap to identify groups of patches that have multiple similarities.

FRAGSTATS is a spatial pattern analysis program developed by landscape ecologists for quantifying the structure (i.e., composition and configuration) of landscapes at multiple scales (see this link to the documentation). Through the lens of a landscape ecologist, a landscape may be considered as an assemblage of patches whose spatial homo/heterogeneity characterize the landscape they comprise. While the patches of interest to landscape ecologists are often habitat types, they may represent any spatial phenomenon, including forest disturbance.

The installation of FRAGSTATS is very straightforward (link to downloads page), and the GUI is friendly! Below I outline the steps for adding data to FRAGSTATS and generating patch metrics:

1) Add a layer. FRAGSTATS accepts raster images in a variety of formats (again, see documentation here). I worked with GeoTIFF (.tif) files representing disturbance patches.

2) Select metrics to calculate. Descriptions of each metric can be found in the documentation.

3) Generate Results. Simply click the  button on the main toolbar, and view the results.

If your goal is to attach these tables back to your input data for mapping/analysis, in a GIS for example, then it is crucial to generate a “patch ID file”. To do this, simply check the box for “Generate patch ID file” under the Analysis parameters tab:

The patch ID file and associated tables will be saved to the directory you choose. Note that here I’ve checked only the box for Patch metrics. The patch ID file will have a suffix of “_id8” appended to whatever name your input file is, and it’s associated extension (“input”_id8.tif). The patch metrics file will have a .patch extension. Open the .patch file in Excel or the spreadsheet editor of your choice, delimit by comma, and save it as a file type that ArcMap will recognize, such as .csv or .txt. I suggest removing the “LID” field which contains the file path where your initial input raster resides.

4) Join output .patch file to patch ID file. In ArcMap, bring in both the patch ID and copy of the patch file in .csv or .txt format. Then, proceed with a tabular join:

Right-click the _id8 file, click Join…in the prompt window that appears choose “Value” for the field in the patch ID file, and PID for the field in the table of patch attributes. Click OK. The patch attributes are now joined to each patch in the patch ID file. Open the attribute table of the patch ID file to verify. Remember to export this file to make the join permanent.

*Note: if you don’t see “Value” as an option for the join field, you may have to run the “Build Raster Attribute Table” tool on your patch ID file.

5) Proceed with Mapping/Analysis!

*Note that the FRAGSTATS tabular outputs are useful in their own right. Below I’ve charted “class” level metrics (as opposed to patch level) that show trends in clear-cut patches over time. In this case, I filtered the disturbance data for clear-cuts only, and had FRAGSTATS generate outputs by year (year is the “class”).