Stand: Edge

The edge raster variable represents the percentage of the stand classified as edge. For this project, edge is defined as a 2 height-class difference between stands. Production of this data layer was a multistep procedure. First a raster of stand height was produced. Topex scripts were run on this raster with a limiting distance of 30 m, or 1 pixel. This identified all height-class differences between stands across the landscape. Positive values indicated edges of shorter stands, and negative values indicated edges of taller stands. The original height grid was also analyzed with Arc9’s zonal range statistics tool. Range statistics defined all edges classified by the height differences between the two adjacent stands. This raster was recoded to display only edges greater than 2 height-class differences. The Topex-generated edge raster and range statistics raster were combined to identify the edges of the taller stands (negative Topex scores) when the height difference between adjacent stands was greater than 2 height classes (range statistic greater than 2). Stands delineated in the GIS database were used as zones to calculate the percentage of edge within the individual stands, and the index was generated directly from these values.