Disturbance and landscape dynamics in the Chequamegon National Forest Wisconsin, USA, from 1972 to 2001

摘要

Land uses, especially harvesting and road building, are considered to be the primary cause of forest fragmentation in many parts of the world. To test this perception, we (1) quantified changes and rates of change in vegetative composition and structure within the Washburn Ranger District in northern Wisconsin using Landsat images, (2) examined changes in landscape structure, (3) assessed changes within the area of road influence (ARI), and (4) investigated changes in landscape composition and structure within the context of forest management activities. Our landscape classifications included six dominant cover types: mixed hardwood (MH), jack pine (JP), red pine (RP), mixed hardwood/conifer (MHC), non-forested bare ground (NFBG), and regenerating forest or shrub (RFS). Increases in NFBG and RFS, by 196% and 28% respectively, reflect expansion of the pine-barrens. Windthrow in the mature hardwoods during the late 1970s and jack pine budworm outbreaks during the mid-1990s correlated with decreases in those classes over the corresponding intervals. A 69% decrease in mean patch size and a 60% increase in edge density reflect increased fragmentation. An inverse relationship existed between the compositional trends of forested (excluding JP) cover types and RFS and NFBG cover types. ARI covered 8% of the landscape affecting species composition within the MH, RFS, and NFBG. Results from this study are key in assessing the links between management activities and ecological consequences and thereby facilitate adaptive management.