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Sacrificing the Ecological Resolution of Vegetation Maps at the Altar of Thematic Accuracy: Assessed Map Accuracies for Hierarchical Vegetation Classifications in the Eastern Great Basin of the Southwest Regional Gap Analysis Project (Sw Regap)

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Abstract:The Southwest Regional Gap Analysis Project (SW ReGAP) improves upon previous GAP projects conducted in Arizona, Colorado, Nevada, New Mexico, and Utah to provide a
consistent, seamless vegetation map for this large and ecologically diverse geographic region. Nevada's component of the land cover mapping effort comprises 15 mapzones, or 291,700 km2. As of October 2003, preliminary field sampling has been completed via road-based sampling and backpacking surveys in all 15 of Nevada's mapzones yielding a data set of 17,000+ sites. Based on plant community data collected in the field, each site is labeled with NVCS alliance and ecological system labels, and a National Land Cover Database (NLCD) label. Site polygons were intersected with 40+ spectral, topographic, climatic, and edaphic datalayers. A set of decision rules ( or land cover models) was generated by the application of a classification/regression tree (CART) algorithm to the plant community label and its associated dependent variables. Land cover models were implemented in Imagine 8.6 image processing software to create classified vegetation maps. Three maps were constructed for each mapping unit at increasing levels of ecological resolution: an NLCD level map (coarsest), and ecological systems map (intermediate), and an alliance level map (finest). Maps have been constructed for the Mojave, Eastern Great Basin, and Lahontan Basin mapping units. Final vegetation maps were assessed for thematic accuracy at each of the three levels of ecological resolution. The NLCD level maps produced the highest thematic accuracy while the alliance level map produced the lowest thematic accuracy. The procedures used in field data collection, land cover modeling, accuracy assessment, and edge-matching adjacent mapping units are illustrated with examples from the east Great Basin mapping unit of east central Nevada.
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Citation:Sajwaj, T. D., W. G. Kepner, D. F. Bradford, and C. T. Herndon. Sacrificing the Ecological Resolution of Vegetation Maps at the Altar of Thematic Accuracy: Assessed Map Accuracies for Hierarchical Vegetation Classifications in the Eastern Great Basin of the Southwest Regional Gap Analysis Project (Sw Regap). Presented at 13th Annual National Gap Analysis Program Meeting, Fort Collins, CO, October 7-10, 2003.
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Contact: Chris Siebert - (702) 798-2234 or siebert.christopher@epa.gov
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Division: Environmental Sciences Division
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Branch: Landscape Ecology Branch
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Product Type: Abstrct/Oral
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Presented: 10/07/2003
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Related Entries:
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Bullet Item Development of Landscape Indicators for Use in Regional Ecological Risk Assessments
spacer Relationship Reason:   A Project of the Product
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