Vegetation Classification and Mapping at Gateway National Recreation Area

Edinger, Gregory; Feldmann, Aissa; Howard, Timothy; Schmid, John; Eastman, Elizabeth; Largay, Ery; Sneddon, Lesley

Vegetation classification and mapping of vegetation associations were conducted at the Gateway National Recreation Area, creating current digital geospatial databases for the park. Thirty-five vegetation associations that occur within the park were identified and described in detail. The diversity of vegetation associations is primarily a result of the following four factors: 1) the geologic history of the region, especially the effect of glaciation; 2) the park’s position on the northeastern U.S. coastal plain; 3) its proximity to the ocean and maritime ecological processes, such as diurnal tides, storm overwash, salt spray, and high winds; and 4) its setting within an urban landscape with an intensive human land use history along with its associated problems, such as invasive species, fragmentation, habitat loss, pollution, channel dredging, land filling, etc. In 2003, a preliminary vegetation map of Gateway National Recreation Area was created showing NY ecological communities (Edinger et al. 2002) that was used to plan the vegetation plot sampling strategy. After plot sampling in 2003 and 2004, statistical analyses were conducted on these data in order to refine the classification and map. Prior to accuracy assessment (AA) field sampling, a revised preliminary map was created showing National Vegetation Classification (NVC) vegetation associations and Anderson Level II land cover classes. This revised map was used in spring 2006 to plan the thematic AA strategy. After AA field sampling in summer 2006, a final map was created in 2007 showing corrected NVC associations and Anderson II land cover classes. Thematic AA for the vegetation association map was calculated with a contingency matrix. The Kappa index for the 2006 revised preliminary map was 0.6201, with the overall percent accuracy calculated as 63.75%. The 2006 revised preliminary map and the final 2007 post-AA maps were created, following the USGS/NPS Vegetation Mapping Program protocols (TNC and ESRI 1994a, 1994b; ESRI et al. 1994). All map polygons, vegetation sampling plots, and AA sampling points were labeled with the NVC vegetation association code, NY ecological community name, and Anderson Level II land cover class and code. A detailed classification was created with global and local descriptions and other relevant information for each NVC association surveyed or mapped at the park. A dichotomous field key was developed for these vegetation associations to assist with field recognition and classification. A CD with all plot and accuracy assessment point photographs taken during this project was compiled. In addition, a separate map of palustrine and estuarine wetlands of the park was created from the final vegetation association map. Despite the degraded landscape and developed areas in and around the park, Gateway National Recreation Area has several vegetation associations with biodiversity significance at the state and global level. The rarest association in the park is the maritime holly forest in the Sandy Hook Unit, New Jersey. At 231 acres it is the largest one of only two known occurrences in the world, with the other located at Sunken Forest on Fire Island National Seashore, New York. The low salt marsh in Jamaica Bay is currently the largest (1,237 acres) example in the state documented by NY Natural Heritage, and the maritime dunes at Breezy Point are of good quality and considered significant from a statewide perspective. All of the vegetation associations at the park provide habitat for a wide array of species and present numerous opportunities for nature study and recreation for visitors.

Vegetation Classification and Mapping at Gateway National Recreation Area

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