Effects of Deicing Salt on Eastern White Pine: Foliar Injury, Growth Suppression and Seasonal Changes in Foliar Concentrations of Sodium and Chloride

Effects of deicing salt on eastern white pine (Pinusstrobus L.) were studied in the field and in the laboratory. Studies in controlled temperature chambers showed that solutions of deicing salt sprayed onto 4-year-old trees induced symptoms of foliar browning similar to those observed on trees growing near highways. Symptoms developed at 15 °C but not at 1.5 °C. The amount of injury that developed after 3 weeks at 15 °C appeared to be directly related to the concentration of sodium and chloride in the leaf tissue. Repeated sampling of foliage from trees adjacent to highway 401 between May 1970 and May 1971 revealed that foliar concentrations of sodium and chloride declined from abnormally high values (up to 1%) in May to 'normal' levels (0.02–0.1%) by August. The rate of loss was proportional to the foliar concentration of these ions. Growth of these trees, measured as bud weight, needle length, needle dry weight, needle bundles per leader, and leaf length, was suppressed on the side of trees exposed to the highway, but this suppression diminished as distance from the highway increased. Annual radial increments to the trunk were appreciably smaller in trees close to the highway than in trees further away. These results support the concept that deicing salt spray injures leaves and reduces growth of eastern white pine growing adjacent to highways that receive deicing salt in the winter.