Two measures of landscape-graph connectivity: assessment across gradients in area and configuration |
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Authors: | Joseph R Ferrari Todd R Lookingbill Maile C Neel |
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Institution: | (1) Appalachian Laboratory, University of Maryland Center for Environmental Science, Frostburg, MD 21532, USA;(2) Department of Plant Science and Landscape Architecture and Department of Entomology, University of Maryland, College Park, MD 20742, USA |
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Abstract: | Landscape connectivity is critical to species persistence in the face of habitat loss and fragmentation. Graph theory is a
well-defined method for quantifying connectivity that has tremendous potential for ecology, but its application has been limited
to a small number of conservation scenarios, each with a fixed proportion of habitat. Because it is important to distinguish
changes in habitat configuration from changes in habitat area in assessing the potential impacts of fragmentation, we investigated
two metrics that measure these different influences on connectivity. The first metric, graph diameter, has been advocated
as a useful measure of habitat configuration. We propose a second area-based metric that combines information on the amount
of connected habitat and the amount of habitat in the largest patch. We calculated each metric across gradients in habitat
area and configuration using multifractal neutral landscapes. The results identify critical connectivity thresholds as a function
of the level of fragmentation and a parallel is drawn between the behavior of graph theory metrics and those of percolation
theory. The combination of the two metrics provides a means for targeting sites most at risk of suffering low potential connectivity
as a result of habitat fragmentation. |
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Keywords: | Connectivity Fragmentation Graph theory Percolation theory Threshold |
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