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USGS - Core Science Analytics, Synthesis, and Library - Gap Analysis Project

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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 GAP National Land Cover data. Forested...
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The Land Cover Data - Version 1.0 represents a highly thematically detailed land cover map of the U.S. The map legend includes types described by NatureServe's Ecological Systems Classification (Comer et al. 2002) as well as land use classes described in the National Land Cover Dataset 2001 (Homer et al. 2007). This version of the land cover data was used to support the Gap Analysis Project's vertebrate species modeling efforts. These data cover the entire continental U.S. and are a continuous data layer. These raster data have a 30 m x 30 m cell resolution. This land cover data set is considered official foundational data for the GAP species modeling process. The data have been made available provisionally to enhance...
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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 GAP National Land Cover data. Forested...
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Some species respond to the amount of canopy cover within a habitat type. The Percent Canopy Cover dataset was derived from the National Land Cover Dataset. The canopy cover database was compiled from the National Land Cover Dataset, and classifies each pixel into 101 possible values (0% - 100%). The canopy density estimate applies to the forest classes only. For further information on Canopy Cover, see http://landcover.usgs.gov/pdf/canopy_density.pdf. This dataset is a continuous canopy cover percentage and covers the entire U.S. These raster data have a 30 m x 30 m cell resolution. This canopy cover data set is considered official foundational data for the GAP species modeling process. The data have been made...
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Water and its location on the landscape are important aspects of a species distribution. A number of water related data layers were used to refine these species models. These include water type (i.e. flowing, open/standing), distance to and from water, and stream flow and underlying gradient. The source for this data was the USGS National Hydrography Dataset (NHD)(USGS 2007). Hydrographic features were divided into three types: flowing water, open/standing water, and wet vegetation. These feature types were extracted from the NHD by selecting the corresponding codes (the FCODE attribute) in datatables and creating seperate datasets for each data type. To facilitate their use in spatial modeling, these feature types...
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