DOI: 10.5066/f7t43rz7
title: USGS Gap Analysis Project Additional Data: Forest/Open + Woodland/Shrubland

description: The ecotone (i.e., edge) between forested and non-forested environments can be a critical aspect of habitat. We grouped land cover types - ecological systems, human land use, and water - (subsequently referred to as map units) into forested, non-forested, and shrubland/woodland land cover types to create unique data layers. These data layers can then be buffered at specified distances to identify species' habitats. Aggregated map units can be compared and contrasted to identify areas of transition between these broad categories. They can also be used to identify core areas or contiguous blocks of similar type (i.e., interior) through buffering. This dataset was derived from the USGS Gap Analysis Project (GAP) National Land Cover data. Forested map units included deciduous forest, evergreen forest, mixed forest, palustrine forested wetland, and estuarine forested wetland. Non-forested map units were defined as water, pasture/hay, agricultural areas, urban/developed, marshes, beaches, etc. Woodland/shrubland map units were defined as those ecological systems and land uses containing a majority of short, scrubby, woody vegetation or sparsely canopied treed vegetation. Forest edge was processed using ESRI Arc Macro Language scripts and reclass tables to facilitate the development of Forest edge. Although scripts were consistent nationwide, the reclass tables were region specific. Forest and nonForest classes are identified in landcover grid with a reclass table, and then focalmajority is used to remove small isolated pixels prior to buffering. Buffering is done with 2 grids; one for exterior buffers (FROM) and one for interior buffers (INTO). The forest/open only ecotone does not consider environments with sparse canopies or scrubby vegetation, therefore this data layer includes woodland and shrubland map units that would otherwise be ignored. This dataset uses 2 data layers in tandem. The forest/open ecotone and the woodlands/shrublands (i.e., wlsl) are calculated individually and then combined to depict a landscape that includes both ecotones. Ecotone Width: This distance represents a symmetrically buffered edge (i.e., 0, 30, 60, 120, 250, 500, and 1000 meters). For example, an ecotone width of 500 meters includes 250 meters into forest and 250 meters into open. Buffer distances - Distances into ecotone (e.g., forest edge): 0, 30, 60, 120, 250, 500, 1000, 2000, 4000, and greater than 4000 meters Distances away ecotone (e.g., forest edge: greater than 4000, 4000, 2000, 1000, 500, 250, 120, 60, 30 and 0 meters These data are divided into 6 regions across the US (Northwest, Southwest, Great Plains, Upper Midwest, Southeast, and Northeast). If you want complete coverage of the entire US, all 6 regional files are needed. These raster data have a 30 m x 30 m cell resolution. No selection of this parameter indicates the species' model is not contingent on an forest edge. GAP used the best information available to create the forest edge ancillary data; however GAP seeks to improve and update these data as new information becomes available.