2018 ASHS Annual Conference

Salinity stress in plants is typically regarded as an issue of dryland and maritime regions. However, salinity stress is also a concern along roadways in inland mesic regions, where winter precipitation and freezing temperatures warrant the use deicing salt. In this context, stormwater runoff has historically been channeled into local streams and rivers, but there are rapidly expanding efforts to divert roadway runoff into green infrastructure elements such as raingardens and bioswales. Salinity could therefore become an increasing challenge as more vegetated stormwater infrastructure systems are installed along roadways. As part of an investigation on plant health in bioswales that capture runoff from a section of Interstate 95 in Philadelphia, we measured soil electrical conductivity (EC) to assess sodium chloride levels across a topographical gradient. In June and August 2017, EC_1:5 was measured in soils beneath 72 focal plants; it ranged from 0.34-0.78 and 0.13-0.80 dS/m, respectively, the highest values of which are indicative of “high” soil salinity. Monthly measurements were made in the spring of 2018 at 18 sampling locations spanning topographically low and high areas. Soils reached “severe” salinity levels in January (EC range = 0.08-2.11 dS/m) and February (0.12-2.85 dS/m), and “extreme” levels in March (0.09-4.2 dS/m). Areas of elevated EC_1:5 correlated spatially with the flow paths of storm water, low lying areas, and depressions where pooling occurs. These results provide support to a hypothesis that salinity stress is contributing to topographic differences in plant growth. Further data collection efforts will determine if high salinity persists in the soil into the growing season, and if water stress and/or toxicity responses are directly evident in plants.