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 rates 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 quarry contributing to major differences in available Ca along the transect over the last decades. Higher supply of Ca changed biogeochemical cycling by increasing pool sizes and fluxes of Ca in foliage, litter, throughfall, forest floor, soil, herbaceous vegetation, and soil solution. Regression analyses of net throughfall was a useful tool for separating between dry deposition and leaching of Ca. Dry deposition rates of particulate Ca declined rapidly with increasing distance from the Ca source. Leaching of Ca from the canopy declined along the gradient according to Ca content of the green foliage during the growing season. Leaching rates as a percentage of the stand's annual requirement indicated a relative shift from solid (litter) toward more solute Ca fluxes reaching the forest floor with increasing Ca availability of the stand.