Watershed analysis of forest fragmentation by clearcuts and roads in a Wyoming forest

Remotely sensed data and a Geographic Information System were used to compa re the effects of clearcutting and road-building on the landscape pattern o f the Bighorn National Forest, in north-central Wyoming. Landscape patterns were quantified for each of 12 watersheds on a series of four maps that di ffered only in the degree of clearcutting and road density. We analyzed sev eral landscape pattern metrics for the landscape as a whole and for the lod gepole pine and spruce/fir cover classes across these maps, and determined the relative effects of clearcutting and road building on the pattern of ea ch watershed. At both the landscape- and cover class-scales, clearcutting a nd road building resulted in increased fragmentation as represented by a di stinct suite of landscape structural changes. Patch core area and mean patc h size decreased, and edge density and patch density increased as a result of clearcuts and roads. Clearcuts and roads simplified patch shapes at the landscape scale, but increased the complexity of lodgepole pine patches. Ro ads appeared to be a more significant agent of change than clearcuts, and r oads which were more evenly distributed across a watershed had a greater ef fect on landscape pattern than did those which were densely clustered. Exam ining individual watersheds allows for the comparison of fragmentation amon g watersheds, as well as across the landscape as a whole. Similar studies o f landscape structure in other National Forests and on other public lands m ay help to identify and prevent further fragmentation of these areas.