Vegetation classification and mapping project report, Lyndon B. Johnson National Historical Park, National Park Service, Southern Plains Network

Cogan, Dan

Lyndon B. Johnson National Historical Park (LYJO) encompasses approximately 674 acres in the Texas Hill Country, approximately 60 miles north of San Antonio and 50 miles west of Austin. This unique terrain supports over 450 species of vascular plants and includes many examples of native plant communities indigenous to this area. The park consists of two districts, the LBJ Ranch District near Stonewall, TX and the Johnson City District in the heart of Johnson City. Both units are managed to preserve and maintain the heritage of Lyndon B. Johnson, the 36th President of the Unites States. To better understand the distribution of the plant assemblages located on these sites, the National Park Service (NPS) Southern Plains Inventory and Monitoring Network (SOPN) started a vegetation mapping and classification effort at LYJO in 2005. A three-year program was initiated to complete the task of mapping and classifying the vegetation at LYJO. Phase one, directed by the Botanical Research Institute of Texas (BRIT) in conjunction with NatureServe developed a vegetation classification using the National Vegetation Classification System (NVCS). Phase two, directed by the U.S. Bureau of Reclamation’s (BOR) Remote Sensing and GIS group in conjunction with Cogan Technology, Inc (CTI) produced a digital vegetation map. To classify the vegetation, 36 representative plots located throughout the approximately 4,600 acre project area (parks + environs) were sampled during the summer of 2005. Analysis of the plot data by NatureServe in the winter of 2005-2006 produced 11 distinct plant associations and alliances, 3 of which were newly described in the National Vegetation Classification (NVC). In addition, CTI described 2 more alliances and 1 distinctive stand of vegetation (i.e. Park Special) that primarily occurred outside of the park boundary in the environs. Descriptions and a field key for all 14 unique plant assemblages for LYJO are included in this report. To produce the digital map, a combination of 1:12,000-scale color infrared digital ortho-imagery acquired in 2003, 1:12,000-scale true color ortho-rectified imagery acquired in 2005, and all of the GPS referenced ground data were used to interpret the complex patterns of vegetation and land-use. All imagery was acquired from the U.S. Department of Agriculture - Farm Service Agency’s Aerial Photography Field Office and the National Agriculture Imagery Program. In the end, 27 map units (14 vegetated and 13 land-use) were developed and directly cross-walked or matched to corresponding plant associations and land-use classes. All of the interpreted and remotely sensed data were converted to Geographic Information System (GIS) databases using ArcGIS© software. Draft maps were printed, field tested, reviewed, and revised. One hundred and thirty three accuracy assessment (AA) data points were collected in 2006 and used to determine the map’s accuracy. After final revisions, the accuracy assessment revealed an overall thematic accuracy of 92%.

Vegetation classification and mapping project report, Lyndon B. Johnson National Historical Park, National Park Service, Southern Plains Network

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