Effects of land-cover change on spatial pattern of forest communities in the Southern Appalachian Mountains (USA)

Understanding the implications of past, present and future patterns of human land use for biodiversity and ecosystem function is increasingly important in landscape ecology. We examined effects of land-use change on four major forest communities of the Southern Appalachian Mountains (USA), and addressed two questions: (1) Are forest communities differentially susceptible to loss and fragmentation due to human land use? (2) Which forest communities are most likely to be affected by projected future land cover changes? In four study landscapes, maps of forest cover for four time periods (1950, 1970, 1990, and projections for 2030) were combined with maps of potential forest types to measure changes in the extent and spatial pattern of northern hardwoods, cove hardwoods, mixed hardwoods, and oak-pine. Overall, forest cover increased and forest fragmentation declined in all four study areas between 1950 and 1990. Among forest community types, cove hardwoods and oak-pine communities were most affected by land-cover change. Relative to its potential, cove hardwoods occupied only 30-40% of its potential area in two study landscapes in the 1950s, and oak-pine occupied similar to 50% of its potential area; cove hardwoods remained reduced in extent and number of patches in the 1990s. Changes in northern hardwoods, which are restricted to high elevations and occur in small patches, were minimal. Mixed hardwoods were the dominant and most highly connected forest community type, occupying between 47 and 70% of each study area. Projected land-cover changes suggest ongoing reforestation in less populated regions but declining forest cover in rapidly developing areas. Building density in forest habitats also increased during the study period and is projected to increase in the future; cove hardwoods and northern hardwoods may be particularly vulnerable. Although increases in forest cover will provide additional habitat for native species, increases in building density within forests may offset some of these gains. Species-rich cove hardwood communities are likely to be most vulnerable to future land-use change.