The small-scale distribution of J. virginiana on Hog island will be examined by extensive ground surveys. Tree locations will be determined using a geographic positioning system (GPS) to identify the specific global coordinates of individual trees and small thickets. The coordinate information will then be entered into a geographic information system (GIS) to plot the sites on a vegetation map of the island. Spatial and temporal variations in plant stress will be identified through measurements of stomatal conductance and xylem pressure potential for representative plants. Variation in soil salinity among J. virginiana will be quantified for soils collected during the ground survey. Soil samples from the tree rhizospheres will be returned to the lab for total chloride analysis. Additionally, samples (N=3) will be collected at 50 m intervals across the island along LTER transects 1, 4 and 5 analyzed for chloride content. Depth to groundwater and groundwater salinity will be measured through existing wells or temporary holes augered across the transect. Transect salinities will be related to elevation (each transect will be surveyed with the Pentax total station) and microtopographic position (e.g. dune ridges, mesic swales, etc.), as well as to position relative to the ocean. This information will be used in a GIS to generate a map of soil salinity and potential plant stress relative to microtopographic position and relative position to the ocean.