EFFECTS OF WATERSHED LIMING ON THE SOIL CHEMISTRY OF WOODS LAKE, NEW-YORK

The effects of watershed liming on the exchange complex of a forest so il were investigated at Woods Lake, in the west-central Adirondack Par k, New York. Attempts to neutralize lake acidity via direct applicatio n of calcite during the 1980's were short-lived due to a short hydraul ic retention time. The Experimental Watershed Liming Study (EWLS) was initiated to investigate watershed base addition as a potentially more long-term strategy for mitigation of lake acidity. In this paper we d iscuss the changes in the exchangeable soil complex which occurred in response to the calcite addition and attempt a mass balance for calcit e applied to the watershed. An extensive sampling program was initiate d for the watershed study. Soil samples were collected from pits prior to and in the two years following treatment to evaluate changes in so il chemistry. Calcite addition significantly altered the exchange comp lex in the organic horizon. Increases in pH caused deprotonation of so il organic matter and increases in cation exchange capacity, providing additional exchange sites for the retention of added calcium. Exchang eable acidity decreased to very low values, allowing the base saturati on of upper organic horizons to increase to nearly 100 percent. Post-t reatment sampling found that approximately 48 percent of the calcite r emained undissolved in the soil's Oe horizon two years later. Dissolut ion of the calcite was affected by field moisture conditions, with gre ater dissolution in wetter areas of the watershed. Mass balances calcu lated for calcium applied to the watershed suggest that only 4 percent of the calcium was removed through the lake outlet. Approximately 96 percent of the calcium applied remained within the watershed; as undis solved calcite, on soil exchange sites or stored in the vegetation, gr oundwater or surface waters of the watershed.