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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)
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.
Impact/Purpose:
The primary objectives of this research are to:
Develop methodologies so that landscape indicator values generated from different sensors on different dates (but in the same areas) are comparable; differences in metric values result from landscape changes and not differences in the sensors;
Quantify relationships between landscape metrics generated from wall-to-wall spatial data and (1) specific parameters related to water resource conditions in different environmental settings across the US, including but not limited to nutrients, sediment, and benthic communities, and (2) multi-species habitat suitability;
Develop and validate multivariate models based on quantification studies;
Develop GIS/model assessment protocols and tools to characterize risk of nutrient and sediment TMDL exceedence;
Complete an initial draft (potentially web based) of a national landscape condition assessment.
This research directly supports long-term goals established in ORDs multiyear plans related to GPRA Goal 2 (Water) and GPRA Goal 4 (Healthy Communities and Ecosystems), although funding for this task comes from Goal 4. Relative to the GRPA Goal 2 multiyear plan, this research is intended to "provide tools to assess and diagnose impairment in aquatic systems and the sources of associated stressors." Relative to the Goal 4 Multiyear Plan this research is intended to (1) provide states and tribes with an ability to assess the condition of waterbodies in a scientifically defensible and representative way, while allowing for aggregation and assessment of trends at multiple scales, (2) assist Federal, State and Local managers in diagnosing the probable cause and forecasting future conditions in a scientifically defensible manner to protect and restore ecosystems, and (3) provide Federal, State and Local managers with a scientifically defensible way to assess current and future ecological conditions, and probable causes of impairments, and a way to evaluate alternative future management scenarios.
Description:
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.