The files linked to this reference are the geospatial data created as part of the completion of the baseline vegetation inventory project for the NPS park unit. Current format is ArcGIS file geodatabase but older formats may exist as shapefiles. We followed methods in Anderson and Merrill (1998) for combining gradient layers into an “ecological land units” map (also referred to as a “biophysical units” map). Our goal was to use this information to create sampling strata that capture the range of environments observed. The Anderson and Merrill (1998) method (implemented as a set of GIS scripts by F. Biasi (2001)) builds an ecological units map by classifying and combining individual environmental gradient maps in a GIS. Maps of aspect, moisture, slope, and slope shape are reclassified and assembled to produce maps of landform units. These landform units are then combined with reclassified elevation and geologic maps to produce a final ecological land units or “ELU” map. We used these methods as a guide to building an ecological land units map for Shenandoah National Park, adapting the procedures for local conditions. Individual steps in the process and maps resulting from intermediate and final stages are described in the report.

The files linked to this reference are the geospatial data created as part of the completion of the baseline vegetation inventory project for the NPS park unit. Current format is ArcGIS file geodatabase but older formats may exist as shapefiles. The map units delineated on the orthophotos were derived from the NVC classification as constrained by the limitations of the photography. We combined the preliminary NVC classification with the aerial photo signatures to determine how many plant associations could be recognized on the photos. In most instances, one NVC association corresponded to one map unit. However, sometimes a plant association could not be recognized consistently on the photos or we could see more detail than was recognized by the classification. These problems were overcome by using two separate but related classifications: 1) the NVC for the plot data and 2) map units for the GIS database. The two were related or “crosswalked” by noting when plant associations were lumped into a single map unit or where when associations were split into multiple map units.

The files linked to this reference are the geospatial data created as part of the completion of the baseline vegetation inventory project for the NPS park unit. Current format is ArcGIS file geodatabase but older formats may exist as shapefiles. The map units delineated on the orthophotos were derived from the NVC classification as constrained by the limitations of the photography. We combined the preliminary NVC classification with the aerial photo signatures to determine how many plant associations could be recognized on the photos. In most instances, one NVC association corresponded to one map unit. However, sometimes a plant association could not be recognized consistently on the photos or we could see more detail than was recognized by the classification. These problems were overcome by using two separate but related classifications: 1) the NVC for the plot data and 2) map units for the GIS database. The two were related or “crosswalked” by noting when plant associations were lumped into a single map unit or where when associations were split into multiple map units.

The files linked to this reference are the geospatial data created as part of the completion of the baseline vegetation inventory project for the NPS park unit. Current format is ArcGIS file geodatabase but older formats may exist as shapefiles. Following the vegetation plot data analysis, the preliminary vegetation map was edited and refined to produce a revised preliminary vegetation map prior to thematic accuracy assessment (AA). Using ArcMap 9.2 (ESRI 1999-2006), polygon boundaries were revised on-screen using the newly acquired aerial orthophotography (digital photomosaic) based on the classification plot data, field observations, classification analyses, aerial photography signatures, and topographic maps. Each polygon was assigned the USNVC Community Element Global (CEGL) code of a preliminary vegetation association based on the information sources listed above. Second, third, and fourth CEGL code choices were entered in cases of uncertainty, or for polygons representing mosaics of two or more vegetation types.

The files linked to this reference are the geospatial data created as part of the completion of the baseline vegetation inventory project for the NPS park unit. Current format is ArcGIS file geodatabase but older formats may exist as shapefiles. Following the vegetation plot data analysis, the preliminary vegetation map was edited and refined to produce a revised preliminary vegetation map prior to thematic accuracy assessment (AA). Using ArcMap 9.2 (ESRI 1999-2006), polygon boundaries were revised on-screen using the newly acquired aerial orthophotography (digital photomosaic) based on the classification plot data, field observations, classification analyses, aerial photography signatures, and topographic maps. Each polygon was assigned the USNVC Community Element Global (CEGL) code of a preliminary vegetation association based on the information sources listed above. Second, third, and fourth CEGL code choices were entered in cases of uncertainty, or for polygons representing mosaics of two or more vegetation types.

The files linked to this reference are the geospatial data created as part of the completion of the baseline vegetation inventory project for the NPS park unit. Current format is ArcGIS file geodatabase but older formats may exist as shapefiles. In order to accommodate the complex vegetation patterns often found in National Park units and generally maintain a minimum mapping unit of 0.5 ha, a three-tiered scheme was developed for attributing vegetation polygons. Where appropriate, secondary and tertiary vegetation classes are added to describe mixed-plant communities within the polygon. Secondary and tertiary classes were especially useful for describing ecotones, and for polygons with a patchwork of communities below the minimum mapping unit size. Final products included seamless park-wide GIS databases in ArcGIS geodatabase and ArcView shapefile formats of detailed overstory vegetation communities, along with vegetation statistics, hardcopy maps and orthophoto images plotted at large scale corresponding to the park area.

The files linked to this reference are the geospatial data created as part of the completion of the baseline vegetation inventory project for the NPS park unit. Current format is ArcGIS file geodatabase but older formats may exist as shapefiles. In order to accommodate the complex vegetation patterns often found in National Park units and generally maintain a minimum mapping unit of 0.5 ha, a three-tiered scheme was developed for attributing vegetation polygons. Where appropriate, secondary and tertiary vegetation classes are added to describe mixed-plant communities within the polygon. Secondary and tertiary classes were especially useful for describing ecotones, and for polygons with a patchwork of communities below the minimum mapping unit size. Final products included seamless park-wide GIS databases in ArcGIS geodatabase and ArcView shapefile formats of detailed overstory vegetation communities, along with vegetation statistics, hardcopy maps and orthophoto images plotted at large scale corresponding to the park area.

The files linked to this reference are the geospatial data created as part of the completion of the baseline vegetation inventory project for the NPS park unit. Current format is ArcGIS file geodatabase but older formats may exist as shapefiles. Following the vegetation plot data analysis, the preliminary vegetation map was edited and refined to produce a revised preliminary vegetation map prior to thematic accuracy assessment. Using ArcMap 9.2 (ESRI 1999-2006), polygon boundaries were revised on screen based on the plot data, field observations, classification analyses, aerial photography signatures, and topographic maps. Each polygon was assigned the NVC Community Element Global (CEGL) code of a preliminary vegetation association based on the information sources listed above. Second, third, and fourth CEGL code choices were entered in cases of uncertainty, or for polygons representing mosaics of two or more types.

The files linked to this reference are the geospatial data created as part of the completion of the baseline vegetation inventory project for the NPS park unit. Current format is ArcGIS file geodatabase but older formats may exist as shapefiles. Following the vegetation plot data analysis, the preliminary vegetation map was edited and refined to produce a revised preliminary vegetation map prior to thematic accuracy assessment. Using ArcMap 9.2 (ESRI 1999-2006), polygon boundaries were revised on screen based on the plot data, field observations, classification analyses, aerial photography signatures, and topographic maps. Each polygon was assigned the NVC Community Element Global (CEGL) code of a preliminary vegetation association based on the information sources listed above. Second, third, and fourth CEGL code choices were entered in cases of uncertainty, or for polygons representing mosaics of two or more types.

The files linked to this reference are the geospatial data created as part of the completion of the baseline vegetation inventory project for the NPS park unit. Current format is ArcGIS file geodatabase but older formats may exist as shapefiles. Just over 698 acres, including 214 acres in the authorized boundary of HOME and an additional 484 acres in the environs, were mapped using ten map classes (Figure 5). This included four land cover classes and six vegetation classes. Of all the map units, the most frequent was Fraxinus pennsylvanica / Ulmus spp. / Celtis occidentalis Forest with 21 polygons. Fraxinus pennsylvanica / Ulmus spp. / Celtis occidentalis Forest was also the most abundant map unit in terms of area other than cropfields in the environs, covering 219 acres (89 hectares) or about 13% of the project area. All of the frequencies for each map unit (i.e., number of polygons) along with acreage per map unit are listed in Table 3. Normally the standard minimum mapping unit for NPS vegetation mapping projects is defined as 0.5 hectare. However this is a nominal unit and due to the small size of HOME and the resolution of the imagery it was reduced to allow for more detail in the mapping. Therefore, 13 of the total 60 polygons were under 0.5 hectare. The average area of polygons for this project was 28.8 acres (11.6 hectares).