Vegetation Classification and Mapping at Colonial National Historical Park, Virginia

Patterson, Karen

Accurate and up-to-date vegetation maps are recognized by the National Park Service (NPS) Inventory and Monitoring Program as one of twelve basic data sets for every national park with significant natural resources. The National Park Service (NPS) and the U.S. Geological Survey (USGS) have put forth standards and protocols for classification and mapping of vegetation communities on NPS lands. The USGS-NPS Vegetation Mapping Program recognizes the United States National Vegetation Classification (USNVC) as the standard vegetation classification to be used in these mapping projects. Vegetation data collected from seven national parks in Virginia were combined with over 2,000 existing plot samples from throughout the Mid-Atlantic Piedmont and Coastal Plain and used to refine the USNVC for the mid-Atlantic region. This classification was used to map and describe the vegetation at the seven national parks in Virginia. This report documents the classification and mapping of vegetation at Colonial National Historical Park. Forty map classes representing 31 USNVC associations, seven nonstandard, park-specific vegetation classes, and seven Anderson Level II land-use categories were used to map the 3,452-ha (8,529-ac) park. Vegetation map classes were determined through extensive field reconnaissance, data collection, and analysis. Leaf-off aerial photography from 2002 served as the base map, and field sampling was conducted from 2003–2005. Spatial data were digitized onscreen over digital orthophoto mosaics created from scanned color infrared, stereo pair 1:6,000 scale aerial photography using a 0.5 hectare minimum mapping unit. The vegetation map for Colonial National Historical Park covers 3498 ha (8644 ac) in and around the park. Transitional vegetation covers 37.4% of the land in the park (1,308.4 ha [3,233.0 ac]). Cultural map classes cover 19.3% (676.6 ha [1671.9 ac]) of the park and include the Anderson land-use categories and other man-made or maintained areas in the park. Tidal wetlands account for approximately 16.3% (568.5 ha [1404.7 ac]) of the park, and nontidal wetlands cover 4.9% (171.9 ha [424.7 ac]). Open water accounts for 2% of the area on the vegetation map. The remaining 20.1% (702.5 ha [1,736.0 ac]) of the park land is mapped as later successional, upland forests. A vegetation map of Colonial National Historical Park was created following the USGS-NPS Vegetation Mapping Program protocols. Vegetation map classes were crosswalked to the Natural Communities of Virginia and to the USNVC in order to provide a regional and global context for the park’s vegetation. One hundred and eighty-three randomly selected accuracy assessment sampling points were collected throughout the park and used to assess the thematic accuracy of the map. The Kappa Index for the final vegetation map was 83.8 ± 4.7%, with an overall accuracy of 84.7%. A field key to the vegetation classes, and detailed descriptions for map classes, or associations within a map class, were developed to assist with field recognition and classification. Additional products associated with this project include leaf-on and leaf-off orthophoto mosaics, a database of vegetation plot data and accuracy assessment data, digital photos of vegetation associations, and spatial data files for the vegetation map, plot sample points, and accuracy assessment sample points with associated Federal Geographic Data Committee (FGDC)-compliant metadata. Products for Colonial National Historical Park and similar national park vegetation mapping projects can be accessed at the USGS-NPS Vegetation Mapping Program website: http://biology.usgs.gov/npsveg/.

Vegetation Classification and Mapping at Colonial National Historical Park, Virginia

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