Transitions in forest fragmentation: implications for restoration opportunities at regional scales |
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Authors: | Wickham James D. Jones K. Bruce Riitters Kurt H. Wade Timothy G. O'Neill Robert V. |
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Affiliation: | (1) U.S. Environmental Protection Agency (MD-56), National Exposure Research Laboratory, Research Triangle Park, NC 27711, USA;(2) U.S. Environmental Protection Agency, National Exposure Research Laboratory, Las Vegas, NV 89119, USA;(3) Biological Resources Division, U.S. Geological Survey, Raleigh, NC 27695, USA;(4) Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA |
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Abstract: | 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. |
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Keywords: | GIS hierarchy land-cover percolation theory scale threshold |
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