Abstract
Budgets of Na, K, Mg, Ca, Al and Si in two forested basins in central Europe indicate that the weathering rate of gneiss and the depletion of exchangeable calcium and magnesium are increased due to acidification caused by high deposition of SO 2 . The production of the pool of exchangeable cations is slower than its depletion. There is a coincidence of a very short time necessary to deplete the topsoil of the exchangeable Ca 2+ and Mg 2+ and the die-back of spruce. These conclusions are derived from a new mass-balance approach that enables a separation of hydrolysis of primary minerals, depletion of exchangeable ions and production of the exchangeable pool of cations in soils from data on elemental budgets in small hydrological basins.