QUANTIFYING SOIL DEVELOPMENT IN HEMLOCK DOMINATED FORESTS

Hemlock woolly adelgid (HWA), an invasive insect, has been killing hemlock trees on the eastern seaboard for decades and is slowly spreading westward. Studies of the ecological impacts of HWA have documented increased sunlight penetration, water and soil temperatures, water flow, nitrification rates, and nitrate transport to streams, which all contribute to the changing ecosystem in these forests. However, it is still poorly understood how the death of hemlock trees may affect the physicochemical properties of soils, soil ecology, and further soil development. The goals of this project were to 1) compare soils from an HWA infected and uninfected forest groves to identify changes in soil physicochemical properties, and 2) quantify soil development at these sites using four weathering indices. Soil samples were collected at two state parks, Robert V. Riddell (RVR) and Mine Kill (MK), in New York State. At the uninfected site of RVR, a standard soil pit was dug by hand, and soil was collected by horizons in duplicates. At MK, both infected and uninfected hemlock groves were sampled in duplicates using a 2-inch hand-auger to the depth of human refusal limit, and the cores were divided by horizons. For each sample, moisture content, pH, electrical conductivity, and extractable cation and anion concentrations are determined using established methods. Preliminary data indicates that the infected sites at MK had decreased concentrations of extractable chloride and sulfate, and increased concentrations of extractable calcium and magnesium. In our ongoing study, X-ray fluorescence spectrometry is used to determine the elemental composition of bulk soil to be able to access the soil development stage and the rates of soil formation. The chemical index of weathering, the chemical index of alteration, the weathering index of Parker, and the plagioclase index of alteration are suitable indices for these soils formed on glaciated sedimentary terrains. Pearson correlation coefficients are obtained for the studied physicochemical parameters and weathering indices for every soil horizon to evaluate soil development factors and processes. This project was partially funded by the Stephen G. Pollock Undergraduate Student Research Grants of the Northeastern Section of GSA.