Canopy leaching, dry deposition, and cycling of calcium in Austrian oak stands as a function of calcium availability and distance from a lime quarry

Three Austrian oak stands were chosen along a 4-km distance gradient from a lime quarry to study effects of Ca availability both on dry deposition rat es and on Ca cycling in these ecosystems. A fourth stand was used as a more regional reference site, some 30 km west of the lime quarry. Calcium bulk precipitation fluxes decreased with increasing distance from the lime quarr y contributing to major differences in available Ca along the transect over the last decades. Higher supply of Ca changed biogeochemical cycling by in creasing pool sizes and fluxes of Ca in foliage, litter, throughfall, fores t floor, soil, herbaceous vegetation, and soil solution. Regression analyse s of net throughfall was a useful tool for separating between dry depositio n and leaching of Ca. Dry deposition rates of particulate Ca declined rapid ly with increasing distance from the Ca source. Leaching of Ca from the can opy declined along the gradient according to Ca content of the green foliag e during the growing season. Leaching rates as a percentage of the stand's annual requirement indicated a relative shift from solid (litter) toward mo re solute Ca fluxes reaching the forest floor with increasing Ca availabili ty of the stand.