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.

Diversity of soil fauna in the canopy and forest floor of a Venezuelan cloud forest

ABSTRACTArboreal and terresterial soil and lilter were sampled for macro-and microinvertebrates at two locations in a Venezuelan cloud forest. Fauna were most abundant in forest floor soil and associated litter. However, media suspended in the canopy and particularly those trapped in bromeliad shoots were most densely populated, while the diversities of the arboreal and terrestrial soil fauna were indistinguishable. Rates of leaf litter decomposition in the arboreal and terrestrial soils were similar, but the arboreal soils contained higher concentrations of mineral nutrients and carbon. Implications of these findings for the definition of soil in humid tropical forests, and related differences between temperate and tropical forests are discussed. The similarities in diversity and differences in species composition between arboreal and terrestrial soil fauna raise questions concerning the evolution of tropical soil fauna, as well as the estimate of global biotic diversity.