Changes in Cu accumulation and fractionation along soil depth in acid soils of vineyards and abandoned vineyards (now forests)

Abstract

This study investigated changes in copper accumulation and fractionation based on the depth of soils obtained from active and abandoned vineyards. Soil samples were collected at different depths in three areas with active and abandoned vineyards, and the concentrations of total copper and copper fractions were measured in these soil samples. Results revealed that in active vineyards, total copper accumulation was the highest in the first layer of soil (depth = 0–2 cm), with concentrations (193–892 mg kg−1) considerably higher than those in the deepest soil layer (depth = 40–50 cm; concentration = 63–71 mg kg−1). This accumulation was significantly correlated with the total carbon concentration in the soil. However, the total copper concentration in abandoned vineyards (84–374 mg kg−1) was the highest in the subsurface layers (depth = 10–15 cm) and was not significantly correlated with the total carbon content. Moreover, the percentage of available copper was lower in abandoned vineyards than in active vineyards. In terms of copper fractionation, the main fraction in active vineyard soil was copper bound to organic matter, whereas the main fraction in abandoned vineyard soil was residual copper. Therefore, vineyard abandonment and its transformation into forest changed the distribution and fractionation of copper based on soil depth, thus decreasing the amount of available copper and improving the soil quality, which could enable new ecosystems.