Abstract
Reductions in fire frequency (RFF) are known to occur in the area adjacent to the rigid-boundary of simulated forest landscapes. Few studies, however, have removed those edge effected regions (EERs), and many others may, thus, have misinterpreted their simulated forest conditions within those unidentified edges. We developed three methods to detect and remove EERs with RFF and applied them to fire frequency maps of 2900 × 2900 grids developed using between 1000 and 1200 fire-year maps. The three methods employed different approaches: scanning, agglomeration, and division, along with the consensus of two and three of those methods. The detected EERs with RFF ranged in mean width from 5.9 to 17.3 km, and occupied 4.9 to 21.3% of the simulated landscapes. Those values are lower than the 40 km buffer width, which occupied 47.5% of the simulated landscape, used in a previous study in this area that based buffer width on length of the largest fire. The maximum width of the EER covaried with wind predominance, indicating it is not possible to prescribe a standard buffer width for all simulation studies. The three edge detection methods differ in their optimality, with the best results provided by a consensus of the three methods. We suggest that future landscape forest simulation studies should, to ensure their results near the rigid boundary are not misrepresentative, simulate an appropriately enlarged study area and then employ edge detection methods to remove the EERs with RFF.
Highlights
Ecological edge effects occur where adjacencies of two or more different ecosystems result in altered ecosystem processes and conditions [1]
Removal of effected regions (EERs) with reduced fire frequency (RFF) is essential in landscape forest simulation studies, to ensure that researchers do not misinterpret their simulated results near the rigid boundaries
The reason that only six of the hundreds of landscape forest simulation studies have removed a buffer may be because methods have not been available to detect EERs with RFF
Summary
Ecological edge effects occur where adjacencies of two or more different ecosystems result in altered ecosystem processes and conditions [1]. In landscape-scale simulations of animal dispersal [7] and forest fires [8] the rigid-boundary edge effects resulted in reduced predictions of, respectively, the occurrence of animals and fires These reductions happen because while the interior of the landscape would receive animals or fires from all directions, the edge of the finite landscape could only receive them from the interior. Many simulated studies have removed the presumed EER in the simulated landscape, called a buffer zone [12] or guard area [11], leaving an embedded space [10] that we will call an interior This method is appropriate to use in landscape forest simulation studies, and is the approach we will develop. The three methods each employ large sample areas, as FF varies stochastically across space, and one of the methods assumes that there is an interior of the simulated forest landscape that does not have an EER with RFF. The three methods will differ in the optimality of their identified EERs with RFF; the optimal method will employ the smallest EER to maximally differentiate the low FR in the edge from the high FR in the interior
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