MESH (landscape level)

Effective Mesh Size (Aggregation metric)

Usage

lsm_l_mesh(landscape, directions = 8)

Arguments

landscape: A categorical raster object: SpatRaster; Raster* Layer, Stack, Brick; stars or a list of SpatRasters.
directions: The number of directions in which patches should be connected: 4 (rook's case) or 8 (queen's case).

Value

tibble

Details

$$MESH = \frac{\sum \limits_{i = 1}^{m} \sum \limits_{j = 1}^{n} a_{ij} ^ 2}{A} * \frac{1} {10000}$$ where $a_{ij}$ is the patch area in square meters and $A$ is the total landscape area in square meters.

The effective mesh size is an 'Aggregation metric'. Because each patch is squared before the sum is calculated and the sum is standardized by the total landscape area, MESH is a relative measure of patch structure. MESH is perfectly, negatively correlated to lsm_l_division.

Because the metric is based on distances or areas please make sure your data is valid using check_landscape.

Units

Hectares

Range

cell size / total area <= MESH <= total area

Behaviour

Equals cellsize/total area if class covers only one cell and equals total area if only one patch is present.

References

McGarigal K., SA Cushman, and E Ene. 2023. FRAGSTATS v4: Spatial Pattern Analysis Program for Categorical Maps. Computer software program produced by the authors; available at the following web site: https://www.fragstats.org

Jaeger, J. A. 2000. Landscape division, splitting index, and effective mesh size: new measures of landscape fragmentation. Landscape ecology, 15(2), 115-130.

Examples

landscape <- terra::rast(landscapemetrics::landscape)
lsm_l_mesh(landscape)
#> # A tibble: 1 × 6
#>   layer level     class    id metric   value
#>   <int> <chr>     <int> <int> <chr>    <dbl>
#> 1     1 landscape    NA    NA mesh   0.00938