Measuring the Abruptness of Patchy Ecotones: A simulation-based Comparison of Patch and Edge Metrics

The use of statistics of landscape pattern to infer ecological process at ecotones requires knowledge of the specific sensitivities of statistics to ecotone characteristics. In this study, sets of patch-based and boundary-based statistics were evaluated to assess their suitability as measures of abruptness on simulated ecotone landscapes. We generated 50 realizations each for 25 groups of ecotones that varied systematically in their degree of abruptness and patchiness. Factorial ANOVA was used to evaluate the sensitivity of statistics to the known differences among the simulated groups. Suitability of each index for measuring abruptness was evaluated using the ANOVA results. The statistics were then ranked in order of their suitability as abruptness statistics based on their sensitivity to abruptness, the consistency of the relationship, and their lack of sensitivity to patchiness. The two best statistics for quantifying abruptness were those we developed based on lattice delineation methods, and are called cumulative boundary elements and boundary element dispersion. The results of this research provide support for studies of ecotone process that rely on the interpretation of patch or boundary statistics.