Assateague Island Seabeach Amaranth Survey Data — 2001 to 2018

Since 2001, Assateague Island has been surveyed for seabeach amaranth. The entire island was surveyed each year from 2001-2015. Since then, only the Maryland portion of the island has been included in the surveys due to a lack of observed plants in years leading up to 2015 (USFWS has undertaken surveys on the Virginia portions of the island in recent years). Typically, groups of individuals 4 to 14 walked the widest portions of the island in a north to south or south to north direction. When large numbers of plants were encountered, searches were conducted by multiple people walking east to west and west to east to investigate locations with small plants (1-2cm sq.). Each year, survey teams started surveys and the beginning of August to be completed before the end of the 3rd week in August. Caging of plants began in 2004 to protect plants from grazing by ungulates. Each year since then preliminary searches for plants (to be caged) began in mid-July. Once found, plants encountered were caged to the extent possible prior to annual surveys. Plants not found before the surveys, were often caged once encountered. Field staff used GPS to obtain plant coordinates (UTM coordinates, NAD83, Zone 18) by standing next to the specimens. Observational data were also collected during the August surveys. Consequently, these represent conditions during the first 3 weeks of August. Following annual surveys, plant location and observations regarding their condition were transcribed from field notebooks and GPS units to a spreadsheet by Assateague Island National Seashore natural resources staff. The spreadsheet was updated annually and was completed by different staff members from year to year. The Data_Set_Credit section includes the names of some of these staff members. The process took place from 2001 to 2018, with the process date representing the most recent work. A note on determining the nature of grazing: Observation of grazing on Seabeach Amaranth was obtained by trained observers. Careful attention was paid to ensure no observer tracks obscured the site. Presence and identification of deer or horse tracks would be observed as well as any type of grazing. An amaranth that was determined to be horse herbivory had to first have horse tracks present, and then it had to appear to have either been pulled from the ground or to have been eaten to an extent that was severe. The grazing habit of deer is less destructive, more frequently smaller portions of the plant would be consumed and sometimes bits of fallen plant material would appear near the amaranth plant. The tracks were the most important aspect in determining the perpetrator of the grazing. When both tracks were found (or no tracks were found) and the quality of the grazing effect did not easily represent the eating habit of the animal, “unknown ungulate” was selected. Regarding insect herbivory, presence of insects was a strong indicator upon closer inspection insect damage would appear as holes or semicircular cuts out of leave margins.

The dataset edited by Benjamin Gutierrez and Emily Sturdivant of the USGS to convert the grazing fields into numerical values to facilitate data analysis. Fields included in the original dataset include: YEAR, New ID, ID, NORTHING, EASTING, GPS Height, AREA, Size Class, Avg. Area for Class, OBSERVER, Caged, Ungulate Grazed, Insect Grazed, Grazed, GPS Unit, Location, COMMENT, Count, Total. Some fields were removed from the original dataset as they were incomplete or not used for subsequent analysis. Fields removed include: GPS Height, Size Class, Avg. Area for Class, COMMENT, Count and Final.

To create the vector spatial dataset, the .csv tabular data was imported into Esri ArcMap (version 10.6) using the "XY Table to Point" geoprocessing tool. Data was identified as North American Datum of 1983 (NAD83) UTM Zone 18N.

Within Esri ArcMap (version 10.6), the coordinate system was updated from projected "NAD_1983_UTM_Zone_18N" to geographic coordinates "GCS_North_American_1983" for publication using ArcToolbox > Data Management Tools > Projections and Transformations > Project. Latitude and longitude coordinates were added to the shapefile dataset ArcToolbox > Data Management Tools > Features > Add XY Coordinates.

The final version of the data, including both geographic (point_x, point_y) and projected coordinates (Easting, Northing) and reduced fields, was exported from a shapefile to a .csv file, by exporting the attribute table within ArcMap, saving as a database (.dbf) file. The .dbf file is then opened using Excel (Office 365), and saved as a comma delimited (.csv) file. Both final datasets include the fields: FID*, Shape*, (*shapefile only) YEAR, New_ID, ID, NORTHING, EASTING, Area_cm2, OBSERVER, Caged, Ung_Grazed, Ins_Grazed, Grazed, GPS_unit, Location, Point_X, and Point_Y.