FOREST ROADS AND LANDSCAPE STRUCTURE IN THE SOUTHERN ROCKY-MOUNTAINS

Roadless areas on public lands may serve as environmental baselines ag ainst which human-caused impacts on landscape structure can be measure d. We examined landscape structure across a gradient of road densities , from no roads to heavily roaded, and across several spatial scales. Our study area was comprised of 46,000 ha on the Roosevelt National Fo rest in north-central Colorado. When forest stands were delineated on the basis of seral stage and covertype, no relationship was evident be tween average stand size and road density. Topography appeared to exer t a greater influence on average stand size than did road density. The re was a significant cant positive con-elation between the fractal dim ension of forest stands and road density across all scales. Early-sera l stands existed in greater proportions adjacent to roads, suggesting that the effects of roads on landscape structure are somewhat localize d. We also looked at changes in landscape structure when stand boundar ies were delineated by roads in addition to covertype and seral stage: Overall, there was a large increase in small stands with simple shape s, concurrent with a decline in the number of stands > 100 ha. We conc lude that attempts to quantify the departure from naturalness in roade d areas requires an understanding of the factors controlling the struc ture of unroaded landscapes, particularly where the influence of topog raphy is great. Because roads in forested landscapes influence a varie ty of biotic and abiotic processes, we suggest that roads should be co nsidered as an inherent component of landscape structure. Furthermore, plans involving both the routing of new roads and the closure of exis ting ones should be designed so as to optimize the structure of landsc ape mosaics, given a set of conservation goals.