THE BIOGEOCHEMICAL EFFECTS OF THE HEMLOCK WOOLLY ADELGID ON SOIL WATER CHEMISTRY

The hemlock woolly adelgid (HWA) is an invasive species that feeds on the sap of hemlock trees, causing mass tree mortality. HWA was first introduced into the eastern United States in the 1950s from China and Japan. The non-native insect currently infests hemlock trees of Mine Kill State Park (MK) and threatens to infest Robert V. Riddell State Park (RVR) in the Catskill Mountains, New York. The likelihood of HWA spreading to RVR is high, as HWA spreads by means of wind, birds, and mammals.

Ecological effects of hemlock mortality have been investigated, but soil chemistry and soil water chemistry have not been studied in New York. The goal of this study is to investigate the biogeochemical effects of HWA on soil water chemistry using samples from two locations in New York (MK in Blenheim; RVR in Davenport). Three sampling sites were established at MK, a HWA infected site (HWA), a HWA uninfected site (NHWA), and a HWA infected and treated with insecticides site (HWAT). Surface water samples were collected at RVR. Field parameters such as pH, electrical conductivity (EC), dissolved oxygen, temperature, and turbidity were measured on site. Samples were collected every week through the summers of 2014 and 2015. In the lab, cation and anion composition of the water samples were determined using spectroscopy and chromatography techniques.

Chloride, sulfate and bicarbonate are the major anions, and calcium, magnesium and sodium are the major cations in both the surface and soil waters at all sites. None of the water samples have detectable phosphate, while nitrate ranges between 0.180 and 2.61 mg/L at MK and non-detectable at RVR. Potassium concentrations are below detection limit for most samples. pH values are close to neutral in all samples, while the EC values are higher in soil water samples than in the surface water samples. Soil water samples have about ten times more bicarbonate than the surface samples. This collected baseline data provides information to determine any biogeochemical changes which may result from infection of HWA.