Small-scale distribution and salinity response of Juniperus virginiana on an Atlantic Coast barrier island

A field and laboratory study examined the hypothesis that the small-scale distribution pattern of Juniperus virginiana on barrier islands is related to salinity patterns and plant responses to salinity. Temporal (May-October) and spatial variability in ground water availability, ground water salinity, and total soil chlorides were quantified across a Virginia barrier island. Groundwater depth and salinity increased throughout the summer; microtopographic position and location on the island also affected soil salinities. Highest salinities occurred near the ocean side beach and bay side marsh, as well as in low lying swales that flood during extreme high tides or storms. Median rooting zone chloride level for J. virginiana was 54 mu g/g. In contrast, laboratory germination and growth studies indicated that J. virginiana was significantly affected only at high salinity levels (1000 and 1400 mu g/g), suggesting that salinity is not the only factor regulating small-scale distribution patterns. The broad tolerance to salinity may account for the abundance of J. virginiana in coastal environments.