Filters: Tags: Deductive Modeling (X)
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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...
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...
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...
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...
Environments dominated by human disturbance such as roads, cities, and the constructed materials that support human habitation have profound effects on species. For most species, this data layer was used to exclude species from a portion of the landscape. However, some species respond favorably to human habitats, therefore this data layer was used in an inclusionary manner. The human impact avoidance dataset describes high exclusion/high inclusion proximity to urban environments, and roads. This dataset was derived from US Census TIGER/Line files and GAP’s National Land Cover Database developed by USGS, in particular the impervious dataset. These data are divided into 6 regions across the US (Northwest, Southwest,...
The Hydrologic Unit Code (HUC) is part of a hierarchical classification system for surface water drainage in the US (Seaber et al. 1987). The numerical code represents a “cataloging unit” of delineation. Vector format (i.e. polygon) data were compiled from United States Geological Survey (USGS) source - the Watershed Boundary Dataset (WBD). For this project the dataset was modified by removing duplicate codes, removing duplicate polygons, and editing the line work to include near shore habitats in both the coast lines and within large water bodies. The coastal polygons were expanded 5 kilometers from landward edges to create a consistent coastal boundary. This altered 12-digit code HUC dataset was used to delineate...
Processing constraints made it impractical to model the species habitat distributions across the full conterminous U.S. in one model. The modeling regions were used to stratify the conterminous U.S. into modeling extents that could be efficiently used in our workflow. The regions were based on grouping of the map zones developed for the National Land Cover Dataset production and were designed to partition the full extent into the minimal number of regions while maximizing the homogeneity of habitats within a region. Two versions of each modeling region were created one in which a buffer was applied to remove boundary issues when calculating metrics based on neighborhoods, and a version used to clip the final model...
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