Landscape Trends in Mid-Atlantic and Southeastern United States Ecoregions

摘要

Landscape pattern and composition metrics are potential indicators for broad-scale monitoring of change and for relating change to human and ecological processes. We used a probability sample of 20-km x 20-km sampling blocks to characterize landscape composition and pattern in five USecoregions: the Middle Atlantic Coastal Plain, Southeastern Plains, Northern Piedmont, Piedmont, and Blue Ridge Moun-tains. Land use/land cover (LULC) data for five dates between 1972 and 2000 were obtained for each sample block. Analy-ses focused on quantifying trends in selected landscape pat-tern metrics by ecoregion and comparing trends in land cover proportions and pattern metrics among ecoregions, Repeated measures analysis of the landscape pattern documented a statistically significant trend in all five ecoregions towards a more fine-grained landscape from the early 1970s through 2000. The ecologically important forest cover class also be-came more fine-grained with time (i.e., more numerous and smaller forest patches). Trends in LULC, forest edge, and for-est percent like adjacencies differed among ecoregions. These results suggest that ecoregions provide a geographically co-herent way to regionalize the story of national land use and land cover change in the United States. This study provides new information on LULC change in the southeast United States, Previous studies of the region from the 1930s to the 1980s showed a decrease in landscape fragmentation and an increase in percent forest, while this study showed an in-crease in forest fragmentation and a loss of forest cover.