Vegetation Classification and Mapping at Sagamore Hill National Historic Site, New York

Edinger, Gregory; Feldmann, Aissa; Howard, Timothy

Vegetation classification and mapping of U.S. National Vegetation Classification associations were conducted at the Sagamore Hill National Historic Site, creating current digital geospatial databases for the park. This study of the Sagamore Hill National Historic Site identified and characterized 10 U.S. National Vegetation Classification associations in detail. The diversity and distribution 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 within a temperate climate; 3) proximity to Long Island Sound and maritime ecological processes, such as diurnal tides, storm overwash, salt spray, and high winds; and 4) the park’s setting within a suburban landscape with a moderately intensive human land use history, along with its associated problems, such as invasive species, fragmentation, habitat loss, and pollution. In 2003, a preliminary vegetation map of Sagamore Hill National Historic Site was created showing NY ecological communities (Edinger et al. 2002) and was used to plan the vegetation plot sampling strategy. After plot sampling in 2003, 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 U.S. National Vegetation Classification (USNVC) vegetation associations and Anderson Level II land cover categories. This revised map was used in spring 2006 to plan the thematic AA strategy. Thematic AA for the vegetation association map was calculated with a contingency matrix. The Kappa index for the 2006 preliminary association map was 0.664, with the overall percent accuracy calculated as 71%±21.1%. The confidence intervals indicate that this accuracy is not statistically different than the USGS/NPS vegetation mapping protocol requirement of 80%. After AA field sampling in summer 2006, a final map was created in 2007 showing corrected USNVC associations and Anderson Level II land cover categories. 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, b; ESRI et al. 1994). All map polygons, vegetation sampling plots, and AA sampling points were labeled with the USNVC vegetation association code and NY ecological community name, or Anderson Level II land cover category and code. A detailed appendix was created with global and local descriptions and other relevant information for each USNVC 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, Sagamore Hill National Historic Site has several vegetation associations that may have conservation value at the local level. The Mid-Atlantic Mesic Mixed Hardwood Forest, or oak - tulip tree forest, on the east facing slope is likely the best remaining example of this type on Cove Neck. In addition, the associations that comprise the salt marsh and maritime dune complex serve as a good remnantexample of what was likely more common around the periphery of Cold Spring Harbor. All of the vegetation associations at the park provide habitat for wildlife and present opportunities for nature study for visitors.

Vegetation Classification and Mapping at Sagamore Hill National Historic Site, New York

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