Kurt H. Riitters

The effect of Appalachian mountaintop mining on interior forest

Southern Appalachian forests are predominantly interior because they are spatially extensive with little disturbance imposed by other uses of the land. Appalachian mountaintop mining increased substantially during the 1990s, posing a threat to the interior character of the forest. We used spatial convolution to identify interior forest at multiple scales on circa 1992 and 2001 land-cover maps of the Southern Appalachians. Our analyses show that interior forest loss was 1.75–5.0 times greater than the direct forest loss attributable to mountaintop mining. Mountaintop mining in the southern Appalachians has reduced forest interior area more extensively than the reduction that would be expected based on changes in overall forest area alone. The loss of Southern Appalachian interior forest is of global significance because of the worldwide rarity of large expanses of temperate deciduous forest.

Transitions in forest fragmentation: implications for restoration opportunities at regional scales

Where the potential natural vegetation is continuous forest (e.g., eastern US), a region can be divided into smaller units (e.g., counties, watersheds), and a graph of the proportion of forest in the largest patch versus the proportion in anthropogenic cover can be used as an index of forest fragmentation. If forests are not fragmented beyond that converted to anthropogenic cover, there would be only one patch in the unit and its proportional size would equal 1 minus the percentage of anthropogenic cover. For a set of 130 watersheds in the mid-Atlantic region, there was a transition in forest fragmentation between 15 and 20% anthropogenic cover. The potential for mitigating fragmentation by connecting two or more disjunct forest patches was low when percent anthropogenic cover was low, highest at moderate proportions of anthropogenic cover, and again low as the proportion of anthropogenic cover increased toward 100%. This fragmentation index could be used to prioritize locations for restoration by targeting watersheds where there would be the greatest increase in the size of the largest forest patch.

Temporal change in forest fragmentation at multiple scales

Previous studies of temporal changes in fragmentation have focused almost exclusively on patch and edge statistics, which might not detect changes in the spatial scale at which forest occurs in or dominates the landscape. We used temporal land-cover data for the Chesapeake Bay region and the state of New Jersey to compare patch-based and area–density scaling measures of fragmentation for detecting changes in the spatial scale of forest that may result from forest loss. For the patch-based analysis, we examined changes in the cumulative distribution of patch sizes. For area–density scaling, we used moving windows to examine changes in dominant forest. We defined dominant forest as a forest parcel (pixel) surrounded by a neighborhood in which forest occupied the majority of pixels. We used >50% and ≥60% as thresholds to define majority. Moving window sizes ranged from 2.25 to 5,314.41xa0hectares (ha). Patch size cumulative distributions changed very little over time, providing no indication that forest loss was changing the spatial scale of forest. Area–density scaling showed that dominant forest was sensitive to forest loss, and the sensitivity increased nonlinearly as the spatial scale increased. The ratio of dominant forest loss to forest loss increased nonlinearly from 1.4 to 1.8xa0at the smallest spatial scale to 8.3 to 11.5xa0at the largest spatial scale. The nonlinear relationship between dominant forest loss and forest loss in these regions suggests that continued forest loss will cause abrupt transitions in the scale at which forest dominates the landscape. In comparison to the Chesapeake Bay region, dominant forest loss in New Jersey was less sensitive to forest loss, which may be attributable the protected status of the New Jersey Pine Barrens.

Landscape correlates of breeding bird richness across the United States mid-Atlantic region

Using a new set of landscape indicator data generated by the U.S.EPA, and a comprehensive breeding bird database from the National Breeding Bird Survey, we evaluated associations between breeding bird richness and landscape characteristics across the entire mid-Atlantic region of the United States. We evaluated how these relationships varied among different groupings (guilds) of birds based on functional, structural, and compositional aspects of individual species demographics. Forest edge was by far the most important landscape attribute affecting the richness of the lumped specialist and generalist guilds; specialist species richness was negatively associated with forest edge and generalist richness was positively associated with forest edge. Landscape variables (indicators) explained a greater proportion of specialist species richness than the generalist guild (46% and 31%, respectively). The lower value in generalists may reflect finer-scale distributions of open habitat that go undetected by the Landsat satellite, open habitats created by roads (the areas from which breeding bird data are obtained), and the lumping of a wide variety of species into the generalist category. A further breakdown of species into 16 guilds showed considerable variation in the response of breeding birds to landscape conditions; forest obligate species had the strongest association with landscape indicators measured in this study (55% of the total variation explained) and forest generalists and open ground nesters the lowest (17% of the total variation explained). The variable response of guild species richness to landscape pattern suggests that one must consider species demographics when assessing the consequences of landscape change on breeding birds.