E&S developed model applications to evaluate effects (and cross-cutting linkages) of multiple stressors on base cation supply in acid-sensitive forested watersheds of western North Carolina, eastern Tennessee, and the Andrew Pickens Ranger District of Sumpter National Forest in South Carolina. Key processes that control watershed responses to acidic deposition, climate, tree harvesting, and liming mitigation were explored using a combination of literature review, evaluation of site specific data, and model simulations. The MAGIC model was used to quantify the extent to which base cation mobilization, leaching, and cycling affect nutrient availability in soils and acid neutralization in soil water and stream water. Critical deposition loads were modeled to evaluate the effects of additional stressors and/or site mitigation on the identified critical loads required to protect stream acid neutralizing capacity (ANC) to differing levels and for differing periods of time. These simulations and comparisons with field data will help in the management of southeastern forests by estimating long-term leaching losses of base cations, with consequent effects on acid neutralization and stream ANC. Project completion date was February 2013.
