Fig. 4

The distribution of shape characteristics by the degree of persistence of unburned islands within fires in the Inland Pacific Northwest from 1984 to 2014. The median value is shown with a dashed line of the same color. (a) The patch size (area) decreases as the degree of persistence (DP) increases until DP = 4, which has the same area as unburned islands with DP = 3. (b) The fractal dimension index is a measure of shape complexity: higher values indicate more complex shapes; lower values indicate more simple shapes (round or square). With each successive fire through which an island remains unburned, the island becomes rounder and simpler until DP = 4, which has the same FRAC as DP = 3