CONTRIBUTION OF ROADS TO FOREST FRAGMENTATION IN THE ROCKY-MOUNTAINS

The contribution of roads to forest fragmentation has not been adequat ely analyzed. We quantified fragmentation due to roads in a 30,213-13- ha section of the Medicine Bow-Routt National Forest in south-eastern Wyoming with several indices of landscape structure using a geographic information system. The number of patches, mean patch area, mean inte rior area, mean area of edge influence, mean patch perimeter, total pe rimeter, and mean patch shape identified patch- and edge-related lands cape changes. Shannon-Wiener diversity, dominance, contagion, contrast , and angular second moment indicated effects on landscape diversity a nd texture. Roads added to forest fragmentation more than clearcuts by dissecting large patches into smaller pieces and by converting forest interior habitat into edge habitat. Edge habitat created by roads was 1.54-1.98 times the edge habitat created by clearcuts. The total land scape area affected by clearcuts and roads was 2.5-3.5 times the actua l area by these disturbances. Fragmentation due to roads could be mini mized if road construction is minimized or rerouted so that its fragme ntation effects are reduced. Geographic information system technology can be used to quantify the potential fragmentation effects of individ ual roads and the cumulative effects of a road network on landscape st ructure.