Vegetation mapping at Fort Frederica National Monument

McManamay, Rachel; Curtis, Anthony; Corbett, Sarah

The Southeast Coast Network (SECN) worked with the support of the National Park Service (NPS) Vegetation Inventory Program (VIP) to describe and map vegetation at Fort Frederica National Monument (FOFR). This mapping effort was accomplished through collaboration with the Southeast regional office of NatureServe (Raleigh/Durham, NC). The mapping area is 192 hectares (474 ac), encompassing the entire boundary of FOFR and an additional buffered area of adjacent private lands. NatureServe ecologists identified plant associations for FOFR and a remote sensing specialist from the SECN completed the vegetation mapping using 1:12,000-scale, color-infrared aerial photography and digital orthophotography. NatureServe collected vegetation and environmental data from four vegetation classification plots, and the remote sensing specialist assessed 10 observation points. The SECN hired and trained Student Conservation Association (SCA) interns to conduct the accuracy assessment (AA), which entailed sampling 74 additional points. Fieldwork and mapping were completed between 2005 and 2012. A total of 12 map classes were developed to map the vegetation and general land cover of FOFR and surroundings, including the following: seven map classes representing natural vegetation at the association level in the National Vegetation Classification System (NVCS), one map class representing cultural vegetation (e.g., developed) in the NVCS, and four map classes representing non-vegetated units (e.g., open water bodies, buildings, roads, etc.). Features were interpreted using 1:12,000 scale digital color-infrared aerial photography (flown 07 May 2011) through heads-up-digitizing in ArcGIS (Version 10, © 2010 Environmental Systems Research Institute, Redlands, California). Polygons were mapped to a 0.5-ha minimum mapping unit (MMU). A geodatabase containing various feature-class layers and tables show the locations of vegetation types and general land cover (vegetation map), vegetation plot samples, AA sites, project boundary extent, and aerial photographic centers. The feature-class layer for the FOFR vegetation map provides 50 polygons of detailed attribute data covering 192 ha, with an average polygon size of 8.9 ha. Of the area mapped, 33 polygons (66%) represent natural vegetation types in the NVCS, encompassing 117 ha (61% of the total map extent). Summary reports generated from the vegetation map layer indicate that the Needlerush High Marsh dominates the vegetated landscape (five polygons covering 60.8 ha), with the Southern Atlantic Coast Salt Marsh comprising a considerable portion of the park (six polygons totaling 31.7 ha). Collectively these associations make-up the extensive salt marsh found within FOFR. A thematic study was conducted on the seven map classes within the boundary of FOFR representing floristic types within the NVCS. Results present an overall accuracy of 92.2% (kappa statistic = 75.2 %) based on data from 74 AA sites.

Vegetation mapping at Fort Frederica National Monument

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