NAME
r3.forestfrag - Computes the forest fragmentation index (Riitters et al. 2000)
KEYWORDS
raster3d,
landscape structure analysis,
vegetation structure analysis,
forest,
fragmentation index,
Riitters
SYNOPSIS
r3.forestfrag
r3.forestfrag --help
r3.forestfrag [-rta] input=name output=name size=number [pf=name] [pff=name] transitional_limit=float patch_limit=float [interior_limit=float] [color=string] [--overwrite] [--help] [--verbose] [--quiet] [--ui]
Flags:
- -r
- Set computational region to input raster map
- -t
- Keep Pf and Pff maps
- -a
- Trim the output map to avoid border effects
- --overwrite
- Allow output files to overwrite existing files
- --help
- Print usage summary
- --verbose
- Verbose module output
- --quiet
- Quiet module output
- --ui
- Force launching GUI dialog
Parameters:
- input=name [required]
- Name of forest raster map (where forest=1, non-forest=0)
- output=name [required]
- Name for output 3D raster map
- size=number [required]
- Moving window size (odd number)
- Options: 3-
- Default: 3
- pf=name
- Name for output Pf (forest area density) raster map
- Proportion of area which is forested (amount of forest)
- pff=name
- Name for output Pff (forest connectivity) raster map
- Conditional probability that neighboring cell is forest
- transitional_limit=float [required]
- transitional_limit
- Default: 0.6
- patch_limit=float [required]
- patch_limit
- Default: 0.4
- interior_limit=float
- interior_limit
- color=string
- Source raster for colorization
- Input and color_input are taken from input and color_input options respectively. The rest is computed using r.slope.aspect
- Options: sambale, riitters, perceptual
- Default: sambale
- sambale: Sambale, Stefan Sylla
- riitters: Riitters et. al 2000
- perceptual: Perceptually uniform
TODO: Create a description specific for 3D version
r.forestfrag Computes the forest fragmentation following
the methodology proposed by Riitters et. al (2000). See
this article for a
detailed explanation.
It follows a "sliding window" algorithm with overlapping windows.
The amount of forest and its occurence as adjacent forest pixels
within fixed- area "moving-windows" surrounding each forest pixel is
measured. The window size is user-defined. The result is stored at
the location of the center pixel. Thus, a pixel value in the derived
map refers to "between-pixel" fragmentation around the corresponding
forest location.
As input it requires a binary map with (1) forest and (0)
non-forest. Obviously, one can replace forest any other land cover
type. If one wants to exclude the influence of a specific land cover
type, e.g., water bodies, it should be classified as no-data (NA) in
the input map. See e.g.,
blog post.
Let Pf be the proportion of pixels in the window that
are forested. Define Pff (strictly) as the proportion of
all adjacent (cardinal directions only) pixel pairs that include at
least one forest pixel, for which both pixels are forested. Pff
thus (roughly) estimates the conditional probability that,
given a pixel of forest, its neighbor is also forest. The
classification model then identifies six fragmentation categories as:
interior: Pf = 1.0
patch: Pf < 0.4
transitional: 0.4 ≤ Pf < 0.6
edge: Pf ≥ 0.6 and Pf - Pff < 0
perforated: Pf ≥ 0.6 and Pf - Pff > 0
undetermined: Pf ≥ 0.6 and Pf = Pff
- The moving window size is user-defined (default=3)
and must be an odd number. If an even number is given the function
will stop with an error message.
- No-data cells are ignored. This means that statistics at the
raster edges are based on fewer cells (smaller) moving windows. If this
is a problem, the user can choose to have the output raster trimmed
with a number of raster cells equal to 1/2 * the size of the moving
window.
- The function respects the region. The user has however the option
to set the region to match the input layer.
Petras, V., Newcomb D. J., Mitasova, H. 2017.
Generalized 3D fragmentation index derived from lidar point clouds.
Open Geospatial Data, Software and Standards 2017 2:9
DOI:
10.1186/s40965-017-0021-8
Riitters, K., J. Wickham, R. O'Neill, B. Jones,
and E. Smith. 2000.
Global-scale patterns of forest fragmentation.
Conservation Ecology 4(2): 3. [online] URL:
http://www.consecol.org/vol4/iss2/art3/
r3.count.categories,
g.region,
r.forestfrag
Vaclav Petras,
NCSU GeoForAll Lab
Paulo van Breugel,
main author of the 2D version
(
r.forestfrag)
SOURCE CODE
Available at:
r3.forestfrag source code
(history)
Latest change: Monday Jan 30 19:52:26 2023 in commit: cac8d9d848299297977d1315b7e90cc3f7698730
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