Fragmentation of a forested Rocky Mountain landscape, 1950–1993 Original Research Article

Patterns of change in landscape structure in a portion of the Hayden District of the Medicine Bow National Forest in southeastern Wyoming have been driven primarily by clearcut logging from 1950 to 1993; no major fires or wind storms have occurred in the study area during this time. Two distinct data sets, created from information in the Resource Information System database of the USDA Forest Service, were used as the basis for a quantitative analysis of landscape change. Forest fragmentation was quantified using a geographical information system (GRASS 4·1) to calculate indices of landscape structure. Increases in number of patches (1012 to 1331), total perimeter (3980 to 4400 km), Shannon diversity (2·36 to 2·63), contrast (2·49 to 2·68), and sum of edges (119·1 to 121·2 km) were accompanied by decreases in mean patch size (29·5 to 22·5 ha), mean patch shape (2·16 to 2·05), mean patch perimeter (3·91 to 3·3 km), dominance (1·04 to 0·81), contagion (4·30 to 4·07), and angular second moment (0·14 to 0·10). The observed trends in landscape pattern indicate increasing forest fragmentation since 1950. The study area landscape in 1993 is more fragmented than the landscape of the Oregon Cascades, now the subject of national attention and restoration action. As in other fragmented landscapes, the results suggest that previous management practices have lacked monitoring and analysis of landscape-scale impacts, indicating that increased attention to the landscape-scale is needed in future management actions.